Abstract

In recent years, an increased interest in the efficacy of intrauterine infusion of autologous platelet-rich plasma (PRP) in women with repeated implantation failure (RIF) has resulted in the publication of 13 randomized controlled trials (RCTs) and 11 meta-analyses. Although these meta-analyses support an increase in pregnancy rates after intrauterine infusion of autologous PRP, the low quality of the available original clinical studies along with concerns regarding their trustworthiness seriously questions their internal validity and does not allow for definitive conclusions to be drawn. In addition, the variability in the definition of RIF used in the individual studies limits their external validity, renders the pooling of the results problematic, and, overall, complicates the extrapolation of the results published. The variability in the definition of RIF has been recently addressed by the ESHRE, which published an evidence-based definition of RIF to facilitate the evaluation of interventions in these patients. Taking into consideration this definition, which identifies a real clinical problem, evaluation of intrauterine infusion of PRP in the published literature has not so far been performed explicitly in patients with RIF. The potential of intrauterine infusion of autologous PRP to improve outcomes for women with RIF remains an important area of research in ART. However, the current evidence is insufficient to inform clinical practice, highlighting the need for well-designed studies to provide clearer guidance.

The problem of repeated implantation failure

Repeated implantation failure (RIF) is generally considered a condition in which good-quality embryos fail to implant after multiple transfers (Coughlan et al., 2014). RIF is a longstanding issue in reproductive medicine, impacting treatment outcomes and presenting persistent challenges in ART. This condition not only affects success rates but also leads to emotional and psychological burdens for patients. Clinically, RIF represents a complex problem for both patients and physicians, as it requires careful consideration of potential underlying causes and personalized treatment approaches. The challenge is further complicated by the lack of a standardized definition, leading to heterogeneity in how RIF is diagnosed and managed. This variation makes it difficult to extrapolate and interpret findings from various interventions that have been attempted, as data are not always applicable to the broader population.

In response to this, ESHRE has introduced good practice recommendations for managing RIF, aimed at standardizing diagnostic and therapeutic approaches and improving patient outcomes.

Interventions proposed for management of RIF

The variation in the definition of RIF makes it difficult to compare therapeutic interventions in this category of patients. Some of the interventions proposed are uterine (e.g. endometrial injury, hysteroscopy, atosiban administration, etc.) (Iakovidou et al., 2023), laboratory (e.g. embryo transfer medium enriched with hyaluronic acid, assisted hatching, etc.), pharmacological treatments proposed to enhance endometrial receptivity (e.g. intramuscular growth hormone, vaginal sildenafil, etc.), technologies aimed at identifying the endometrial window of implantation (Simón et al., 2020), and immunomodulatory therapies (e.g. intravenous immunoglobulin, low-molecular-weight heparin, intrauterine autologous platelet-rich plasma (PRP) infusion, etc.) (Busnelli et al., 2021).

Is intrauterine infusion of autologous PRP in RIF patients the answer?

In recent years, the use of intrauterine infusion of autologous PRP in women with RIF has been the focus of interest (Shalma et al., 2023). PRP is a volume of plasma, obtained by centrifugation of patient’s blood, that has a platelet count above baseline. With the intrauterine infusion of autologous PRP, numerous proteins, growth factors (GFs), and cytokines stored in the platelet, act on the endometrium through the promotion of cell proliferation and neoangiogenesis, enhancing the probability of implantation (Bos-Mikich et al., 2019; Lin et al., 2021). The use of autologous PRP has increased in popularity during recent years in parallel with an increased understanding of the role of its GFs in tissue regeneration (Gonçalves et al., 2020).

Thirteen randomized controlled trials (RCTs) and 12 meta-analyses have so far been performed to evaluate the use of intrauterine infusion of autologous PRP in women with RIF (Tables 1 and 2).

Table 1.

Meta-analyses evaluating intrauterine infusion of autologous PRP in RIF patients.

Meta-analysis, yearRIF population: participants (studies)Studies included in the meta-analysis
Probability of pregnancy
RCTs: n First authorNon RCTs: n First authorEffect measure 95% CI n=RIF patients
Busnelli et al., 2021195(2)
  • Clinical pregnancy

  • RR 2.45

  • 1.55–3.86

  • n = 195

Li et al., 20221629(10)
  • Clinical pregnancy

  • RR 1.79

  • 1.55–2.06

  • n = 1629

  • Live birth

  • RR 2.92

  • 2.22–3.85

  • n = 878

Liu et al., 20221219(8)
  • Clinical pregnancy OR 2.24

  • 1.41–3.54

  • n = 1219

  • Live birth

  • OR 5.76

  • 1.55–21.44

  • n = 791

Kong et al., 2023958(7)
  • Clinical pregnancy

  • OR 0.41**

  • 0.26–0.66

  • n = 878

  • Live birth

  • OR 0.27**

  • 0.07–0.97

  • n = 593

Anitua et al., 2023893(9)
  • Clinical pregnancy

  • RR 2.18

  • 1.76–2.70

  • n = 893

  • Live birth

  • RR 3.36

  • 0.84–13.45

  • n = 523

Deng et al., 20231555(10)
  • Clinical pregnancy

  • RR 1.96

  • 1.67–2.31

  • n = 1405

  • Live birth

  • RR 2.83

  • 1.45–5.52

  • n = 871

Hu et al., 2023678(4)
  • Clinical pregnancy

  • RR 2.46

  • 1.93–3.12

  • n = 678

  • Live birth

  • RR: 7.03

  • 3.91–12.66

  • n = 433

Maged et al., 2023Unclear* (12)
  • Clinical pregnancy

  • OR 2.54

  • 1.61–4.02

  • n = 416

  • Live birth

  • OR 2.36

  • 0.15–36.35

  • n = 130

Panda et al., 2023335(4)
  • Clinical pregnancy RR: 1.88

  • 1.17–3.03

  • n = 335

Soliman et al., 20231038(8)
  • Clinical pregnancy RR 2.35

  • 1.92–2.88

  • n = 981

  • Live birth

  • RR 4.03

  • 1.29–12.63

  • n = 553

Shalma et al., 2023Unclear*
  • Clinical pregnancy

  • RR: 1.83

  • 1.49–2.24

  • n = 1772

  • Live birth

  • RR: 2.54

  • 1.36–4.73

  • n = 1003

Vaidakis et al., 2024824(9)
  • Clinical pregnancy (for the one RCT judged at low risk of bias)

  • OR 1.55

  • 0.64–3.76

  • n = 94

  • Live birth or ongoing pregnancy

  • (for the one RCT judged at low risk of bias)

  • OR 1.10

  • 0.38–3.14

  • n = 94

Meta-analysis, yearRIF population: participants (studies)Studies included in the meta-analysis
Probability of pregnancy
RCTs: n First authorNon RCTs: n First authorEffect measure 95% CI n=RIF patients
Busnelli et al., 2021195(2)
  • Clinical pregnancy

  • RR 2.45

  • 1.55–3.86

  • n = 195

Li et al., 20221629(10)
  • Clinical pregnancy

  • RR 1.79

  • 1.55–2.06

  • n = 1629

  • Live birth

  • RR 2.92

  • 2.22–3.85

  • n = 878

Liu et al., 20221219(8)
  • Clinical pregnancy OR 2.24

  • 1.41–3.54

  • n = 1219

  • Live birth

  • OR 5.76

  • 1.55–21.44

  • n = 791

Kong et al., 2023958(7)
  • Clinical pregnancy

  • OR 0.41**

  • 0.26–0.66

  • n = 878

  • Live birth

  • OR 0.27**

  • 0.07–0.97

  • n = 593

Anitua et al., 2023893(9)
  • Clinical pregnancy

  • RR 2.18

  • 1.76–2.70

  • n = 893

  • Live birth

  • RR 3.36

  • 0.84–13.45

  • n = 523

Deng et al., 20231555(10)
  • Clinical pregnancy

  • RR 1.96

  • 1.67–2.31

  • n = 1405

  • Live birth

  • RR 2.83

  • 1.45–5.52

  • n = 871

Hu et al., 2023678(4)
  • Clinical pregnancy

  • RR 2.46

  • 1.93–3.12

  • n = 678

  • Live birth

  • RR: 7.03

  • 3.91–12.66

  • n = 433

Maged et al., 2023Unclear* (12)
  • Clinical pregnancy

  • OR 2.54

  • 1.61–4.02

  • n = 416

  • Live birth

  • OR 2.36

  • 0.15–36.35

  • n = 130

Panda et al., 2023335(4)
  • Clinical pregnancy RR: 1.88

  • 1.17–3.03

  • n = 335

Soliman et al., 20231038(8)
  • Clinical pregnancy RR 2.35

  • 1.92–2.88

  • n = 981

  • Live birth

  • RR 4.03

  • 1.29–12.63

  • n = 553

Shalma et al., 2023Unclear*
  • Clinical pregnancy

  • RR: 1.83

  • 1.49–2.24

  • n = 1772

  • Live birth

  • RR: 2.54

  • 1.36–4.73

  • n = 1003

Vaidakis et al., 2024824(9)
  • Clinical pregnancy (for the one RCT judged at low risk of bias)

  • OR 1.55

  • 0.64–3.76

  • n = 94

  • Live birth or ongoing pregnancy

  • (for the one RCT judged at low risk of bias)

  • OR 1.10

  • 0.38–3.14

  • n = 94

N; number of patients, OR; odds ratio, PRP; platelet-rich plasma, RCT; randomized controlled trial, RIF; repeated implantation failure, RR; risk ratio.

*

Unclear total number of studies and/or population included in the analysis for RIF patients.

**

Better with PRP.

1

Cited by Busnelli as Nazari et al., 2019 and Zamaniyan et al., 2021.

2

Cited by Li as Nazari et al.,2020, Nazari et al., 2022, and Zamaniyan et al., 2021.

3

Cited by Liu as Nazari et al., 2019, Nazari et al., 2021, and Zamaniyan et al., 2021.

4

Cited by Kong as Nazari et al., 2020, Nazari et al., 2022, and Zamaniyan et al., 2021.

5

Cited by Anitua as Nazari et al., 2019, Nazari et al., 2020, Nazari et al., 2021, and Zamaniyan et al., 2021.

6

Cited by Deng as Nazari et al., 2020, Nazari et al., 2022 and Zamaniyan et al., 2021.

7

Cited by Hu as Nazari et al., 2020, Nazari et al., 2022 and Zamaniyan et al., 2021.

8

Cited by Panda as Nazari et al., 2019 and Zamaniyan et al., 2021.

9

Cited by Soliman as Nazari et al., 2019, Nazari et al., 2020, Nazari et al., 2022 (1), Nazari et al., 2022 (2), Zamaniyan et al., 2021.

10

Cited by Shalma as Nazari et al., 2020, Nazari et al., 2022b and Zamaniyan et al., 2021.

11

Cited by Vaidakis as Zamaniyan et al., 2021.

Table 1.

Meta-analyses evaluating intrauterine infusion of autologous PRP in RIF patients.

Meta-analysis, yearRIF population: participants (studies)Studies included in the meta-analysis
Probability of pregnancy
RCTs: n First authorNon RCTs: n First authorEffect measure 95% CI n=RIF patients
Busnelli et al., 2021195(2)
  • Clinical pregnancy

  • RR 2.45

  • 1.55–3.86

  • n = 195

Li et al., 20221629(10)
  • Clinical pregnancy

  • RR 1.79

  • 1.55–2.06

  • n = 1629

  • Live birth

  • RR 2.92

  • 2.22–3.85

  • n = 878

Liu et al., 20221219(8)
  • Clinical pregnancy OR 2.24

  • 1.41–3.54

  • n = 1219

  • Live birth

  • OR 5.76

  • 1.55–21.44

  • n = 791

Kong et al., 2023958(7)
  • Clinical pregnancy

  • OR 0.41**

  • 0.26–0.66

  • n = 878

  • Live birth

  • OR 0.27**

  • 0.07–0.97

  • n = 593

Anitua et al., 2023893(9)
  • Clinical pregnancy

  • RR 2.18

  • 1.76–2.70

  • n = 893

  • Live birth

  • RR 3.36

  • 0.84–13.45

  • n = 523

Deng et al., 20231555(10)
  • Clinical pregnancy

  • RR 1.96

  • 1.67–2.31

  • n = 1405

  • Live birth

  • RR 2.83

  • 1.45–5.52

  • n = 871

Hu et al., 2023678(4)
  • Clinical pregnancy

  • RR 2.46

  • 1.93–3.12

  • n = 678

  • Live birth

  • RR: 7.03

  • 3.91–12.66

  • n = 433

Maged et al., 2023Unclear* (12)
  • Clinical pregnancy

  • OR 2.54

  • 1.61–4.02

  • n = 416

  • Live birth

  • OR 2.36

  • 0.15–36.35

  • n = 130

Panda et al., 2023335(4)
  • Clinical pregnancy RR: 1.88

  • 1.17–3.03

  • n = 335

Soliman et al., 20231038(8)
  • Clinical pregnancy RR 2.35

  • 1.92–2.88

  • n = 981

  • Live birth

  • RR 4.03

  • 1.29–12.63

  • n = 553

Shalma et al., 2023Unclear*
  • Clinical pregnancy

  • RR: 1.83

  • 1.49–2.24

  • n = 1772

  • Live birth

  • RR: 2.54

  • 1.36–4.73

  • n = 1003

Vaidakis et al., 2024824(9)
  • Clinical pregnancy (for the one RCT judged at low risk of bias)

  • OR 1.55

  • 0.64–3.76

  • n = 94

  • Live birth or ongoing pregnancy

  • (for the one RCT judged at low risk of bias)

  • OR 1.10

  • 0.38–3.14

  • n = 94

Meta-analysis, yearRIF population: participants (studies)Studies included in the meta-analysis
Probability of pregnancy
RCTs: n First authorNon RCTs: n First authorEffect measure 95% CI n=RIF patients
Busnelli et al., 2021195(2)
  • Clinical pregnancy

  • RR 2.45

  • 1.55–3.86

  • n = 195

Li et al., 20221629(10)
  • Clinical pregnancy

  • RR 1.79

  • 1.55–2.06

  • n = 1629

  • Live birth

  • RR 2.92

  • 2.22–3.85

  • n = 878

Liu et al., 20221219(8)
  • Clinical pregnancy OR 2.24

  • 1.41–3.54

  • n = 1219

  • Live birth

  • OR 5.76

  • 1.55–21.44

  • n = 791

Kong et al., 2023958(7)
  • Clinical pregnancy

  • OR 0.41**

  • 0.26–0.66

  • n = 878

  • Live birth

  • OR 0.27**

  • 0.07–0.97

  • n = 593

Anitua et al., 2023893(9)
  • Clinical pregnancy

  • RR 2.18

  • 1.76–2.70

  • n = 893

  • Live birth

  • RR 3.36

  • 0.84–13.45

  • n = 523

Deng et al., 20231555(10)
  • Clinical pregnancy

  • RR 1.96

  • 1.67–2.31

  • n = 1405

  • Live birth

  • RR 2.83

  • 1.45–5.52

  • n = 871

Hu et al., 2023678(4)
  • Clinical pregnancy

  • RR 2.46

  • 1.93–3.12

  • n = 678

  • Live birth

  • RR: 7.03

  • 3.91–12.66

  • n = 433

Maged et al., 2023Unclear* (12)
  • Clinical pregnancy

  • OR 2.54

  • 1.61–4.02

  • n = 416

  • Live birth

  • OR 2.36

  • 0.15–36.35

  • n = 130

Panda et al., 2023335(4)
  • Clinical pregnancy RR: 1.88

  • 1.17–3.03

  • n = 335

Soliman et al., 20231038(8)
  • Clinical pregnancy RR 2.35

  • 1.92–2.88

  • n = 981

  • Live birth

  • RR 4.03

  • 1.29–12.63

  • n = 553

Shalma et al., 2023Unclear*
  • Clinical pregnancy

  • RR: 1.83

  • 1.49–2.24

  • n = 1772

  • Live birth

  • RR: 2.54

  • 1.36–4.73

  • n = 1003

Vaidakis et al., 2024824(9)
  • Clinical pregnancy (for the one RCT judged at low risk of bias)

  • OR 1.55

  • 0.64–3.76

  • n = 94

  • Live birth or ongoing pregnancy

  • (for the one RCT judged at low risk of bias)

  • OR 1.10

  • 0.38–3.14

  • n = 94

N; number of patients, OR; odds ratio, PRP; platelet-rich plasma, RCT; randomized controlled trial, RIF; repeated implantation failure, RR; risk ratio.

*

Unclear total number of studies and/or population included in the analysis for RIF patients.

**

Better with PRP.

1

Cited by Busnelli as Nazari et al., 2019 and Zamaniyan et al., 2021.

2

Cited by Li as Nazari et al.,2020, Nazari et al., 2022, and Zamaniyan et al., 2021.

3

Cited by Liu as Nazari et al., 2019, Nazari et al., 2021, and Zamaniyan et al., 2021.

4

Cited by Kong as Nazari et al., 2020, Nazari et al., 2022, and Zamaniyan et al., 2021.

5

Cited by Anitua as Nazari et al., 2019, Nazari et al., 2020, Nazari et al., 2021, and Zamaniyan et al., 2021.

6

Cited by Deng as Nazari et al., 2020, Nazari et al., 2022 and Zamaniyan et al., 2021.

7

Cited by Hu as Nazari et al., 2020, Nazari et al., 2022 and Zamaniyan et al., 2021.

8

Cited by Panda as Nazari et al., 2019 and Zamaniyan et al., 2021.

9

Cited by Soliman as Nazari et al., 2019, Nazari et al., 2020, Nazari et al., 2022 (1), Nazari et al., 2022 (2), Zamaniyan et al., 2021.

10

Cited by Shalma as Nazari et al., 2020, Nazari et al., 2022b and Zamaniyan et al., 2021.

11

Cited by Vaidakis as Zamaniyan et al., 2021.

Table 2.

Methodological characteristics of RCTs evaluating intrauterine infusion of autologous PRP in patients with RIF.

Study, year, journalStudy periodPRP nNo PRP nRandomization methodAllocation concealmentBlindingSample size calculationPrimary outcomeEffect of PRP on the probability of pregnancy: PRP vs no PRP PFinancial support
2018–20192525The patients were randomly assigned the numbers 1–50; those with an even number were assigned to the control group and those with an odd number were assigned to the treatment groupNot reportedNot reported
  • Not

  • reported

Unclear
  • Chemical pregnancy rate

  • 28.0% vs 36.0%,

  • P = 0.830

  • Clinical pregnancy rate*

  • 28.0% vs 24.0%,

  • P = 0.830

None
September 2020–May 20213535Simple random samplingNot reportedNot blindedPerformedEndometrial thickness
  • Clinical pregnancy rate

  • Odds ratio: 0.319**,

  • P < 0.050

None
May 2017–December 20195959Sealed envelopes randomizationSealed envelopesTriple-blindPerformedUnclear
  • Chemical pregnancy rate

  • 43.8% vs 26.1%,

  • P = 0.073

  • Clinical pregnancy rate (4 weeks)

  • 39.6% vs 26.1%,

  • P = 0.164

  • Clinical pregnancy rate (7 weeks)

  • 35.4% vs 26.1%,

  • P = 0.320

  • Ongoing pregnancy rate

  • 16.7% vs 4.3%,

  • P = 0.053

  • Live birth rate

  • 18.8% vs 17.4%,

  • P = 0.864

Jihad-e Daneshgahi Organization, East Azerbaijan, Iran.
Not reported4040Randomization table, block size of 6Not reportedSingle-blindPerformedUnclear
  • Pregnancy rate

  • 12.5% vs 2.5%,

  • P = 0.464

  • Live birth rate

  • 12.5% vs 0.0%,

  • P = 0.054

Ahvaz Jundishapur University of Medical Sciences
Not reported5050Not reportedNot reportedDouble-blindNot reportedUnclear
  • Pregnancy rate

  • 20.0% vs 13.3%,

  • P = 0.620

Not reported
20194545Blocked randomizationNot concealedNot reportedNot reportedUnclear
  • Chemical pregnancy rate

  • 40.0% vs 27.0%,

  • P = 0.192

  • Clinical pregnancy rate

  • 33.0% vs 24.0%,

  • P = 0.410

None
2016–20174948Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Chemical pregnancy rate

  • 53.1% vs 27.1%,

  • P = 0.009

  • Clinical pregnancy rate

  • 44.9% vs 16.7%,

  • P = 0.003

Research department of the school of medicine Shahid Beheshti University of Medical Sciences
July 2018–March 20197575Not reportedNot reportedNot reported
  • Not

  • reported

Positive β-hCG rate 12 days following ET
  • Positive β-HCG rate

  • 43.0% vs 15.0%,

  • P < 0.001

Not reported
February 2016–January 20196060Random number tableNot reportedSingle-blindPerformed
  • Clinical

  • pregnancy, implantation

  • rates

  • Clinical pregnancy rate

  • 48.3% vs 23.3%,

  • P ≤ 0.001

  • Chemical pregnancy rate

  • 33.3% vs 16.7%,

  • P = 0.057

  • Ongoing pregnancy rate

  • 46.7% vs 11.7%,

  • P ≤ 0.001

Not reported
December 2018–October 20215555Computer generated simple random tables in a 1:1 ratioNot concealedNot-blinded
  • Not

  • reported

Positive hCG, 14 days following ET
  • Chemical pregnancy rate

  • 34.6% vs 26.9%,

  • P = 0.400

  • Clinical pregnancy rate

  • 16.8% vs 10.9%,

  • P=ns

Not reported
August 2019–June 20215252Not reportedNot reportedNot reported
  • Not

  • reported

Unclear
  • Clinical pregnancy rate

  • 45.8% vs 22.9%,

  • P = 0.011

  • Chemical pregnancy rate

  • 52.1% vs 33.3%,

  • P = 0.038

None
October 2017–April 20206060Block randomizationNot reportedNot blindedNot reportedUnclear
  • Clinical pregnancy rate

  • 51.7% vs 26.7%,

  • P = 0.005

  • Chemical pregnancy rate

  • 0.0% vs 3.3%,

  • P = 0.490

  • Ongoing pregnancy rate

  • 48.3% vs 25.0%,

  • P = 0.008

  • Live birth rate

  • 58.3% vs 28.3%,

  • P = 0.001

Tehran University of Medical Sciences
2018–2020209209Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Clinical pregnancy rate

  • 49.0% vs 19.3%,

  • P < 0.001

  • Chemical pregnancy rate

  • 51.5% vs 24.9%,

  • P < 0.001

  • Live birth rate

  • 39.3% vs 5.6%,

  • P < 0.001

Not reported
Study, year, journalStudy periodPRP nNo PRP nRandomization methodAllocation concealmentBlindingSample size calculationPrimary outcomeEffect of PRP on the probability of pregnancy: PRP vs no PRP PFinancial support
2018–20192525The patients were randomly assigned the numbers 1–50; those with an even number were assigned to the control group and those with an odd number were assigned to the treatment groupNot reportedNot reported
  • Not

  • reported

Unclear
  • Chemical pregnancy rate

  • 28.0% vs 36.0%,

  • P = 0.830

  • Clinical pregnancy rate*

  • 28.0% vs 24.0%,

  • P = 0.830

None
September 2020–May 20213535Simple random samplingNot reportedNot blindedPerformedEndometrial thickness
  • Clinical pregnancy rate

  • Odds ratio: 0.319**,

  • P < 0.050

None
May 2017–December 20195959Sealed envelopes randomizationSealed envelopesTriple-blindPerformedUnclear
  • Chemical pregnancy rate

  • 43.8% vs 26.1%,

  • P = 0.073

  • Clinical pregnancy rate (4 weeks)

  • 39.6% vs 26.1%,

  • P = 0.164

  • Clinical pregnancy rate (7 weeks)

  • 35.4% vs 26.1%,

  • P = 0.320

  • Ongoing pregnancy rate

  • 16.7% vs 4.3%,

  • P = 0.053

  • Live birth rate

  • 18.8% vs 17.4%,

  • P = 0.864

Jihad-e Daneshgahi Organization, East Azerbaijan, Iran.
Not reported4040Randomization table, block size of 6Not reportedSingle-blindPerformedUnclear
  • Pregnancy rate

  • 12.5% vs 2.5%,

  • P = 0.464

  • Live birth rate

  • 12.5% vs 0.0%,

  • P = 0.054

Ahvaz Jundishapur University of Medical Sciences
Not reported5050Not reportedNot reportedDouble-blindNot reportedUnclear
  • Pregnancy rate

  • 20.0% vs 13.3%,

  • P = 0.620

Not reported
20194545Blocked randomizationNot concealedNot reportedNot reportedUnclear
  • Chemical pregnancy rate

  • 40.0% vs 27.0%,

  • P = 0.192

  • Clinical pregnancy rate

  • 33.0% vs 24.0%,

  • P = 0.410

None
2016–20174948Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Chemical pregnancy rate

  • 53.1% vs 27.1%,

  • P = 0.009

  • Clinical pregnancy rate

  • 44.9% vs 16.7%,

  • P = 0.003

Research department of the school of medicine Shahid Beheshti University of Medical Sciences
July 2018–March 20197575Not reportedNot reportedNot reported
  • Not

  • reported

Positive β-hCG rate 12 days following ET
  • Positive β-HCG rate

  • 43.0% vs 15.0%,

  • P < 0.001

Not reported
February 2016–January 20196060Random number tableNot reportedSingle-blindPerformed
  • Clinical

  • pregnancy, implantation

  • rates

  • Clinical pregnancy rate

  • 48.3% vs 23.3%,

  • P ≤ 0.001

  • Chemical pregnancy rate

  • 33.3% vs 16.7%,

  • P = 0.057

  • Ongoing pregnancy rate

  • 46.7% vs 11.7%,

  • P ≤ 0.001

Not reported
December 2018–October 20215555Computer generated simple random tables in a 1:1 ratioNot concealedNot-blinded
  • Not

  • reported

Positive hCG, 14 days following ET
  • Chemical pregnancy rate

  • 34.6% vs 26.9%,

  • P = 0.400

  • Clinical pregnancy rate

  • 16.8% vs 10.9%,

  • P=ns

Not reported
August 2019–June 20215252Not reportedNot reportedNot reported
  • Not

  • reported

Unclear
  • Clinical pregnancy rate

  • 45.8% vs 22.9%,

  • P = 0.011

  • Chemical pregnancy rate

  • 52.1% vs 33.3%,

  • P = 0.038

None
October 2017–April 20206060Block randomizationNot reportedNot blindedNot reportedUnclear
  • Clinical pregnancy rate

  • 51.7% vs 26.7%,

  • P = 0.005

  • Chemical pregnancy rate

  • 0.0% vs 3.3%,

  • P = 0.490

  • Ongoing pregnancy rate

  • 48.3% vs 25.0%,

  • P = 0.008

  • Live birth rate

  • 58.3% vs 28.3%,

  • P = 0.001

Tehran University of Medical Sciences
2018–2020209209Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Clinical pregnancy rate

  • 49.0% vs 19.3%,

  • P < 0.001

  • Chemical pregnancy rate

  • 51.5% vs 24.9%,

  • P < 0.001

  • Live birth rate

  • 39.3% vs 5.6%,

  • P < 0.001

Not reported

ET, Embryo transfer; N, number of patients; P, P-value; PRP, platelet-rich plasma; RCT, randomized controlled trial; RIF, repeated implantation failure; vs, versus.

*

Different results presented in tables and in abstract/main text.

**

Better with PRP.

Table 2.

Methodological characteristics of RCTs evaluating intrauterine infusion of autologous PRP in patients with RIF.

Study, year, journalStudy periodPRP nNo PRP nRandomization methodAllocation concealmentBlindingSample size calculationPrimary outcomeEffect of PRP on the probability of pregnancy: PRP vs no PRP PFinancial support
2018–20192525The patients were randomly assigned the numbers 1–50; those with an even number were assigned to the control group and those with an odd number were assigned to the treatment groupNot reportedNot reported
  • Not

  • reported

Unclear
  • Chemical pregnancy rate

  • 28.0% vs 36.0%,

  • P = 0.830

  • Clinical pregnancy rate*

  • 28.0% vs 24.0%,

  • P = 0.830

None
September 2020–May 20213535Simple random samplingNot reportedNot blindedPerformedEndometrial thickness
  • Clinical pregnancy rate

  • Odds ratio: 0.319**,

  • P < 0.050

None
May 2017–December 20195959Sealed envelopes randomizationSealed envelopesTriple-blindPerformedUnclear
  • Chemical pregnancy rate

  • 43.8% vs 26.1%,

  • P = 0.073

  • Clinical pregnancy rate (4 weeks)

  • 39.6% vs 26.1%,

  • P = 0.164

  • Clinical pregnancy rate (7 weeks)

  • 35.4% vs 26.1%,

  • P = 0.320

  • Ongoing pregnancy rate

  • 16.7% vs 4.3%,

  • P = 0.053

  • Live birth rate

  • 18.8% vs 17.4%,

  • P = 0.864

Jihad-e Daneshgahi Organization, East Azerbaijan, Iran.
Not reported4040Randomization table, block size of 6Not reportedSingle-blindPerformedUnclear
  • Pregnancy rate

  • 12.5% vs 2.5%,

  • P = 0.464

  • Live birth rate

  • 12.5% vs 0.0%,

  • P = 0.054

Ahvaz Jundishapur University of Medical Sciences
Not reported5050Not reportedNot reportedDouble-blindNot reportedUnclear
  • Pregnancy rate

  • 20.0% vs 13.3%,

  • P = 0.620

Not reported
20194545Blocked randomizationNot concealedNot reportedNot reportedUnclear
  • Chemical pregnancy rate

  • 40.0% vs 27.0%,

  • P = 0.192

  • Clinical pregnancy rate

  • 33.0% vs 24.0%,

  • P = 0.410

None
2016–20174948Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Chemical pregnancy rate

  • 53.1% vs 27.1%,

  • P = 0.009

  • Clinical pregnancy rate

  • 44.9% vs 16.7%,

  • P = 0.003

Research department of the school of medicine Shahid Beheshti University of Medical Sciences
July 2018–March 20197575Not reportedNot reportedNot reported
  • Not

  • reported

Positive β-hCG rate 12 days following ET
  • Positive β-HCG rate

  • 43.0% vs 15.0%,

  • P < 0.001

Not reported
February 2016–January 20196060Random number tableNot reportedSingle-blindPerformed
  • Clinical

  • pregnancy, implantation

  • rates

  • Clinical pregnancy rate

  • 48.3% vs 23.3%,

  • P ≤ 0.001

  • Chemical pregnancy rate

  • 33.3% vs 16.7%,

  • P = 0.057

  • Ongoing pregnancy rate

  • 46.7% vs 11.7%,

  • P ≤ 0.001

Not reported
December 2018–October 20215555Computer generated simple random tables in a 1:1 ratioNot concealedNot-blinded
  • Not

  • reported

Positive hCG, 14 days following ET
  • Chemical pregnancy rate

  • 34.6% vs 26.9%,

  • P = 0.400

  • Clinical pregnancy rate

  • 16.8% vs 10.9%,

  • P=ns

Not reported
August 2019–June 20215252Not reportedNot reportedNot reported
  • Not

  • reported

Unclear
  • Clinical pregnancy rate

  • 45.8% vs 22.9%,

  • P = 0.011

  • Chemical pregnancy rate

  • 52.1% vs 33.3%,

  • P = 0.038

None
October 2017–April 20206060Block randomizationNot reportedNot blindedNot reportedUnclear
  • Clinical pregnancy rate

  • 51.7% vs 26.7%,

  • P = 0.005

  • Chemical pregnancy rate

  • 0.0% vs 3.3%,

  • P = 0.490

  • Ongoing pregnancy rate

  • 48.3% vs 25.0%,

  • P = 0.008

  • Live birth rate

  • 58.3% vs 28.3%,

  • P = 0.001

Tehran University of Medical Sciences
2018–2020209209Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Clinical pregnancy rate

  • 49.0% vs 19.3%,

  • P < 0.001

  • Chemical pregnancy rate

  • 51.5% vs 24.9%,

  • P < 0.001

  • Live birth rate

  • 39.3% vs 5.6%,

  • P < 0.001

Not reported
Study, year, journalStudy periodPRP nNo PRP nRandomization methodAllocation concealmentBlindingSample size calculationPrimary outcomeEffect of PRP on the probability of pregnancy: PRP vs no PRP PFinancial support
2018–20192525The patients were randomly assigned the numbers 1–50; those with an even number were assigned to the control group and those with an odd number were assigned to the treatment groupNot reportedNot reported
  • Not

  • reported

Unclear
  • Chemical pregnancy rate

  • 28.0% vs 36.0%,

  • P = 0.830

  • Clinical pregnancy rate*

  • 28.0% vs 24.0%,

  • P = 0.830

None
September 2020–May 20213535Simple random samplingNot reportedNot blindedPerformedEndometrial thickness
  • Clinical pregnancy rate

  • Odds ratio: 0.319**,

  • P < 0.050

None
May 2017–December 20195959Sealed envelopes randomizationSealed envelopesTriple-blindPerformedUnclear
  • Chemical pregnancy rate

  • 43.8% vs 26.1%,

  • P = 0.073

  • Clinical pregnancy rate (4 weeks)

  • 39.6% vs 26.1%,

  • P = 0.164

  • Clinical pregnancy rate (7 weeks)

  • 35.4% vs 26.1%,

  • P = 0.320

  • Ongoing pregnancy rate

  • 16.7% vs 4.3%,

  • P = 0.053

  • Live birth rate

  • 18.8% vs 17.4%,

  • P = 0.864

Jihad-e Daneshgahi Organization, East Azerbaijan, Iran.
Not reported4040Randomization table, block size of 6Not reportedSingle-blindPerformedUnclear
  • Pregnancy rate

  • 12.5% vs 2.5%,

  • P = 0.464

  • Live birth rate

  • 12.5% vs 0.0%,

  • P = 0.054

Ahvaz Jundishapur University of Medical Sciences
Not reported5050Not reportedNot reportedDouble-blindNot reportedUnclear
  • Pregnancy rate

  • 20.0% vs 13.3%,

  • P = 0.620

Not reported
20194545Blocked randomizationNot concealedNot reportedNot reportedUnclear
  • Chemical pregnancy rate

  • 40.0% vs 27.0%,

  • P = 0.192

  • Clinical pregnancy rate

  • 33.0% vs 24.0%,

  • P = 0.410

None
2016–20174948Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Chemical pregnancy rate

  • 53.1% vs 27.1%,

  • P = 0.009

  • Clinical pregnancy rate

  • 44.9% vs 16.7%,

  • P = 0.003

Research department of the school of medicine Shahid Beheshti University of Medical Sciences
July 2018–March 20197575Not reportedNot reportedNot reported
  • Not

  • reported

Positive β-hCG rate 12 days following ET
  • Positive β-HCG rate

  • 43.0% vs 15.0%,

  • P < 0.001

Not reported
February 2016–January 20196060Random number tableNot reportedSingle-blindPerformed
  • Clinical

  • pregnancy, implantation

  • rates

  • Clinical pregnancy rate

  • 48.3% vs 23.3%,

  • P ≤ 0.001

  • Chemical pregnancy rate

  • 33.3% vs 16.7%,

  • P = 0.057

  • Ongoing pregnancy rate

  • 46.7% vs 11.7%,

  • P ≤ 0.001

Not reported
December 2018–October 20215555Computer generated simple random tables in a 1:1 ratioNot concealedNot-blinded
  • Not

  • reported

Positive hCG, 14 days following ET
  • Chemical pregnancy rate

  • 34.6% vs 26.9%,

  • P = 0.400

  • Clinical pregnancy rate

  • 16.8% vs 10.9%,

  • P=ns

Not reported
August 2019–June 20215252Not reportedNot reportedNot reported
  • Not

  • reported

Unclear
  • Clinical pregnancy rate

  • 45.8% vs 22.9%,

  • P = 0.011

  • Chemical pregnancy rate

  • 52.1% vs 33.3%,

  • P = 0.038

None
October 2017–April 20206060Block randomizationNot reportedNot blindedNot reportedUnclear
  • Clinical pregnancy rate

  • 51.7% vs 26.7%,

  • P = 0.005

  • Chemical pregnancy rate

  • 0.0% vs 3.3%,

  • P = 0.490

  • Ongoing pregnancy rate

  • 48.3% vs 25.0%,

  • P = 0.008

  • Live birth rate

  • 58.3% vs 28.3%,

  • P = 0.001

Tehran University of Medical Sciences
2018–2020209209Computer generated simple random tables in a 1:1 ratioNot reportedSingle-blindPerformedUnclear
  • Clinical pregnancy rate

  • 49.0% vs 19.3%,

  • P < 0.001

  • Chemical pregnancy rate

  • 51.5% vs 24.9%,

  • P < 0.001

  • Live birth rate

  • 39.3% vs 5.6%,

  • P < 0.001

Not reported

ET, Embryo transfer; N, number of patients; P, P-value; PRP, platelet-rich plasma; RCT, randomized controlled trial; RIF, repeated implantation failure; vs, versus.

*

Different results presented in tables and in abstract/main text.

**

Better with PRP.

In the most recent systematic review and meta-analysis, which pooled data from RCTs, non-RCTs, and cohort studies, significantly higher clinical pregnancy (RR: 1.83, 95% CI: 1.49–2.24, P < 0.001) and live birth rates (RR: 2.54, 95% CI: 1.36–4.73, P = 0.003) were reported in women with RIF who underwent intrauterine infusion of autologous PRP compared with those who did not (Shalma et al., 2023). The positive effect of PRP on the achievement of pregnancy in the meta-analysis by Shalma et al. (2023) was also present in all previously published meta-analyses (Table 1).

The latest Cochrane review evaluating the role of PRP in assisted reproduction analyzed all studies published until January 2023 (regardless of risk of bias) reporting very low-certainty evidence about the effect of intrauterine PRP compared with placebo or no intervention on live birth or ongoing pregnancy (OR 2.38, 95% CI: 1.16–4.86; I2=54%; six studies, 564 women) and on clinical pregnancy (OR 2.22, 95% CI: 1.50–3.27; I2=24%; nine studies, 824 women).When only data from RCTs judged at low risk of bias were analyzed, the results show no statistically significant benefit for either live birth or ongoing pregnancy (OR 1.10, 95% CI: 0.38–3.14; one study, 94 women) or clinical pregnancy (OR 1.55, 95% CI: 0.64–3.76; one study, 94 women) (Table 1). Authors reported that overall, the risk of bias was high for most outcomes, owing to unclear descriptions of the randomization process, inadequate management of missing outcome data, and selective reporting (Vaidakis et al., 2024).

Can the available evidence evaluating intrauterine infusion of autologous PRP in RIF patients be trusted?

Are RCTs evaluating intrauterine infusion of autologous PRP in RIF patients of adequate quality and trustworthiness?

The included studies were critically assessed, employing the Cochrane risk-of-bias tool for randomized trials (RoB 2) and the Trustworthiness in Randomized Clinical Trials (TRACT) Screening Checklist (Supplementary Figs S1 and S2, Supplementary Table S1, Supplementary Data Files S1 and S2). All the available RCTs evaluating intrauterine infusion of autologous PRP in RIF patients (Table 3) have been found to present major concerns in at least one of the domains evaluated in the TRACT Screening Checklist (governance, plausibility in the intervention usage, timeframe, drop-out rates, baseline characteristics) (Supplementary Table S1, Supplementary Data File S2).

Table 3.

Problems in the RCTs evaluating intrauterine infusion of autologous PRP in patients with RIF.

Study, year, JournalTitleProblems identified
The effect of PRP on the achievement of pregnancy during frozen embryo transfer in women with a history of failed implantation
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No inclusion/exclusion criteria

  5. No definition of RIF

The effect of autologous PRP treatment on IVF/intracytoplasmic sperm injection and its impact on the endometrium and clinical pregnancy rate
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No definition of RIF

  5. Discrepancy in inclusion and exclusion criterial; in inclusion criteria EMT 0.4–0.7 cm but in exclusion EMT <0.7 cm

  6. No information regarding the time PRP was administered

The effect of PRP on the improvement of pregnancy results in repeated implantation failure: a RCT
  1. Retrospective registration

  2. Protocol was updated twice after registration with no clear reason

  3. Different methods of blinding between original protocol registered and the updates

Effects of intrauterine autologous PRP infusions on outcomes in women with repetitive IVF failures: a prospective randomized study
  1. No information regarding the recruitment period

  2. Change of the inclusion criteria during the study period. Women <40 years of age with at least one failure in the IVF process were included in the registered protocol however infertile women with at least two IVF failures and age below 41 years in the manuscript

  3. Discrepancy between the inclusion criteria in the flow chart (at least two IVF failures with age below 45 years) and in the main text (women with ‘at least two IVF failures and age below 41 years’.)

Effects of autologous PRP in women with repeated implantation failure undergoing assisted reproduction
  1. Wrong registration ID reported

  2. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript(patients with at least 2 cycle of IVF failures & at least six good-quality embryos transferred in previous cycles in the registered protocol and infertile women with a history of RIF who had failed to achieve clinical pregnancy despite having four good-quality embryos transferred, and were candidates for IVF/ICSI or freeze embryo transfer cycles, aged <40 years with BMI < 30 kg/m2 in manuscript)

  3. Unclear whether fresh or frozen cycles were studied

  4. Although according to the protocol women with uterine abnormalities were excluded, the analysis performed incorporates patients with Asherman’s syndrome

  5. No flow diagram

  6. No description of the method of randomization

  7. Pregnancy rates reported do not match with the number of pregnancies reported

Evaluation of the effect of intrauterine injection of PRP on the pregnancy rate of patients with a history of implantation failure in the IVF cycle
  1. No information regarding patient enrolment and allocation

  2. No flow chart is present

The effects of autologous PRP in repeated implantation failure: a RCT
  1. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript (female age below 40 years is an additional inclusion criterion in the published manuscript while patients with thin endometrium that were included in the registered protocol appeared not be included in the published study)

  2. Discrepancy regarding randomization method between the registered protocol and the published manuscript (registered as a single center, RCT with balanced randomization but published study reported ‘Randomization was carried out using computer-generated simple random tables in a 1:1 ratio’.)

  3. Unclear protocol used regarding the use of sham catheter

PRP in RIF, hope or hype? A prospective randomized controlled study
  1. Retrospective registration of the study

  2. No information regarding the method of randomization used, patient allocation, enrollment, and statistical analysis

Effect of PRP on pregnancy outcomes in infertile women with RIF: a RCT
  1. The study was registered as not-blinded but published as blinded

  2. The number patients lost to follow up is significantly different between the two groups compared

  3. Women above 40 years of age and those with BMI > 30 were excluded as per protocol of the study but shown in the flow chart and included in the intention-to-treat analysis

Intrauterine infusion of autologous PRP before frozen embryo transfer in patients with prior implantation failure: a randomized controlled study
  1. Although the study evaluated women with RIF more than 50% of the patients (55/110) had only a single embryo transfer failure

Autologous intrauterine PRP instillation in repeated implantation failure in assisted reproductive techniques.
  1. No registration ID

  2. Discrepancy regarding the number of previous failed attempts between the registered protocol and the published manuscript

  3. Unclear inclusion criteria

Efficacy of the intrauterine infusion of PRP on pregnancy outcomes in patients with repeated implantation failure: a randomized control trial
  1. No registration ID

  2. No adequate information regarding the randomization method used

The effects of autologous PRP on pregnancy outcomes in repeated implantation failure patients undergoing frozen embryo transfer: a RCT
  1. Same registration ID with the study by Nazari et al. (2019)

  2. Unclear protocol used regarding the use of sham catheter

  3. No information regarding patient allocation and concealment

Study, year, JournalTitleProblems identified
The effect of PRP on the achievement of pregnancy during frozen embryo transfer in women with a history of failed implantation
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No inclusion/exclusion criteria

  5. No definition of RIF

The effect of autologous PRP treatment on IVF/intracytoplasmic sperm injection and its impact on the endometrium and clinical pregnancy rate
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No definition of RIF

  5. Discrepancy in inclusion and exclusion criterial; in inclusion criteria EMT 0.4–0.7 cm but in exclusion EMT <0.7 cm

  6. No information regarding the time PRP was administered

The effect of PRP on the improvement of pregnancy results in repeated implantation failure: a RCT
  1. Retrospective registration

  2. Protocol was updated twice after registration with no clear reason

  3. Different methods of blinding between original protocol registered and the updates

Effects of intrauterine autologous PRP infusions on outcomes in women with repetitive IVF failures: a prospective randomized study
  1. No information regarding the recruitment period

  2. Change of the inclusion criteria during the study period. Women <40 years of age with at least one failure in the IVF process were included in the registered protocol however infertile women with at least two IVF failures and age below 41 years in the manuscript

  3. Discrepancy between the inclusion criteria in the flow chart (at least two IVF failures with age below 45 years) and in the main text (women with ‘at least two IVF failures and age below 41 years’.)

Effects of autologous PRP in women with repeated implantation failure undergoing assisted reproduction
  1. Wrong registration ID reported

  2. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript(patients with at least 2 cycle of IVF failures & at least six good-quality embryos transferred in previous cycles in the registered protocol and infertile women with a history of RIF who had failed to achieve clinical pregnancy despite having four good-quality embryos transferred, and were candidates for IVF/ICSI or freeze embryo transfer cycles, aged <40 years with BMI < 30 kg/m2 in manuscript)

  3. Unclear whether fresh or frozen cycles were studied

  4. Although according to the protocol women with uterine abnormalities were excluded, the analysis performed incorporates patients with Asherman’s syndrome

  5. No flow diagram

  6. No description of the method of randomization

  7. Pregnancy rates reported do not match with the number of pregnancies reported

Evaluation of the effect of intrauterine injection of PRP on the pregnancy rate of patients with a history of implantation failure in the IVF cycle
  1. No information regarding patient enrolment and allocation

  2. No flow chart is present

The effects of autologous PRP in repeated implantation failure: a RCT
  1. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript (female age below 40 years is an additional inclusion criterion in the published manuscript while patients with thin endometrium that were included in the registered protocol appeared not be included in the published study)

  2. Discrepancy regarding randomization method between the registered protocol and the published manuscript (registered as a single center, RCT with balanced randomization but published study reported ‘Randomization was carried out using computer-generated simple random tables in a 1:1 ratio’.)

  3. Unclear protocol used regarding the use of sham catheter

PRP in RIF, hope or hype? A prospective randomized controlled study
  1. Retrospective registration of the study

  2. No information regarding the method of randomization used, patient allocation, enrollment, and statistical analysis

Effect of PRP on pregnancy outcomes in infertile women with RIF: a RCT
  1. The study was registered as not-blinded but published as blinded

  2. The number patients lost to follow up is significantly different between the two groups compared

  3. Women above 40 years of age and those with BMI > 30 were excluded as per protocol of the study but shown in the flow chart and included in the intention-to-treat analysis

Intrauterine infusion of autologous PRP before frozen embryo transfer in patients with prior implantation failure: a randomized controlled study
  1. Although the study evaluated women with RIF more than 50% of the patients (55/110) had only a single embryo transfer failure

Autologous intrauterine PRP instillation in repeated implantation failure in assisted reproductive techniques.
  1. No registration ID

  2. Discrepancy regarding the number of previous failed attempts between the registered protocol and the published manuscript

  3. Unclear inclusion criteria

Efficacy of the intrauterine infusion of PRP on pregnancy outcomes in patients with repeated implantation failure: a randomized control trial
  1. No registration ID

  2. No adequate information regarding the randomization method used

The effects of autologous PRP on pregnancy outcomes in repeated implantation failure patients undergoing frozen embryo transfer: a RCT
  1. Same registration ID with the study by Nazari et al. (2019)

  2. Unclear protocol used regarding the use of sham catheter

  3. No information regarding patient allocation and concealment

EMT, endometrial thickness; ID, identity document; ITT, intention-to-treat; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure.

Table 3.

Problems in the RCTs evaluating intrauterine infusion of autologous PRP in patients with RIF.

Study, year, JournalTitleProblems identified
The effect of PRP on the achievement of pregnancy during frozen embryo transfer in women with a history of failed implantation
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No inclusion/exclusion criteria

  5. No definition of RIF

The effect of autologous PRP treatment on IVF/intracytoplasmic sperm injection and its impact on the endometrium and clinical pregnancy rate
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No definition of RIF

  5. Discrepancy in inclusion and exclusion criterial; in inclusion criteria EMT 0.4–0.7 cm but in exclusion EMT <0.7 cm

  6. No information regarding the time PRP was administered

The effect of PRP on the improvement of pregnancy results in repeated implantation failure: a RCT
  1. Retrospective registration

  2. Protocol was updated twice after registration with no clear reason

  3. Different methods of blinding between original protocol registered and the updates

Effects of intrauterine autologous PRP infusions on outcomes in women with repetitive IVF failures: a prospective randomized study
  1. No information regarding the recruitment period

  2. Change of the inclusion criteria during the study period. Women <40 years of age with at least one failure in the IVF process were included in the registered protocol however infertile women with at least two IVF failures and age below 41 years in the manuscript

  3. Discrepancy between the inclusion criteria in the flow chart (at least two IVF failures with age below 45 years) and in the main text (women with ‘at least two IVF failures and age below 41 years’.)

Effects of autologous PRP in women with repeated implantation failure undergoing assisted reproduction
  1. Wrong registration ID reported

  2. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript(patients with at least 2 cycle of IVF failures & at least six good-quality embryos transferred in previous cycles in the registered protocol and infertile women with a history of RIF who had failed to achieve clinical pregnancy despite having four good-quality embryos transferred, and were candidates for IVF/ICSI or freeze embryo transfer cycles, aged <40 years with BMI < 30 kg/m2 in manuscript)

  3. Unclear whether fresh or frozen cycles were studied

  4. Although according to the protocol women with uterine abnormalities were excluded, the analysis performed incorporates patients with Asherman’s syndrome

  5. No flow diagram

  6. No description of the method of randomization

  7. Pregnancy rates reported do not match with the number of pregnancies reported

Evaluation of the effect of intrauterine injection of PRP on the pregnancy rate of patients with a history of implantation failure in the IVF cycle
  1. No information regarding patient enrolment and allocation

  2. No flow chart is present

The effects of autologous PRP in repeated implantation failure: a RCT
  1. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript (female age below 40 years is an additional inclusion criterion in the published manuscript while patients with thin endometrium that were included in the registered protocol appeared not be included in the published study)

  2. Discrepancy regarding randomization method between the registered protocol and the published manuscript (registered as a single center, RCT with balanced randomization but published study reported ‘Randomization was carried out using computer-generated simple random tables in a 1:1 ratio’.)

  3. Unclear protocol used regarding the use of sham catheter

PRP in RIF, hope or hype? A prospective randomized controlled study
  1. Retrospective registration of the study

  2. No information regarding the method of randomization used, patient allocation, enrollment, and statistical analysis

Effect of PRP on pregnancy outcomes in infertile women with RIF: a RCT
  1. The study was registered as not-blinded but published as blinded

  2. The number patients lost to follow up is significantly different between the two groups compared

  3. Women above 40 years of age and those with BMI > 30 were excluded as per protocol of the study but shown in the flow chart and included in the intention-to-treat analysis

Intrauterine infusion of autologous PRP before frozen embryo transfer in patients with prior implantation failure: a randomized controlled study
  1. Although the study evaluated women with RIF more than 50% of the patients (55/110) had only a single embryo transfer failure

Autologous intrauterine PRP instillation in repeated implantation failure in assisted reproductive techniques.
  1. No registration ID

  2. Discrepancy regarding the number of previous failed attempts between the registered protocol and the published manuscript

  3. Unclear inclusion criteria

Efficacy of the intrauterine infusion of PRP on pregnancy outcomes in patients with repeated implantation failure: a randomized control trial
  1. No registration ID

  2. No adequate information regarding the randomization method used

The effects of autologous PRP on pregnancy outcomes in repeated implantation failure patients undergoing frozen embryo transfer: a RCT
  1. Same registration ID with the study by Nazari et al. (2019)

  2. Unclear protocol used regarding the use of sham catheter

  3. No information regarding patient allocation and concealment

Study, year, JournalTitleProblems identified
The effect of PRP on the achievement of pregnancy during frozen embryo transfer in women with a history of failed implantation
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No inclusion/exclusion criteria

  5. No definition of RIF

The effect of autologous PRP treatment on IVF/intracytoplasmic sperm injection and its impact on the endometrium and clinical pregnancy rate
  1. No registration

  2. No flow diagram

  3. No description of method of randomization

  4. No definition of RIF

  5. Discrepancy in inclusion and exclusion criterial; in inclusion criteria EMT 0.4–0.7 cm but in exclusion EMT <0.7 cm

  6. No information regarding the time PRP was administered

The effect of PRP on the improvement of pregnancy results in repeated implantation failure: a RCT
  1. Retrospective registration

  2. Protocol was updated twice after registration with no clear reason

  3. Different methods of blinding between original protocol registered and the updates

Effects of intrauterine autologous PRP infusions on outcomes in women with repetitive IVF failures: a prospective randomized study
  1. No information regarding the recruitment period

  2. Change of the inclusion criteria during the study period. Women <40 years of age with at least one failure in the IVF process were included in the registered protocol however infertile women with at least two IVF failures and age below 41 years in the manuscript

  3. Discrepancy between the inclusion criteria in the flow chart (at least two IVF failures with age below 45 years) and in the main text (women with ‘at least two IVF failures and age below 41 years’.)

Effects of autologous PRP in women with repeated implantation failure undergoing assisted reproduction
  1. Wrong registration ID reported

  2. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript(patients with at least 2 cycle of IVF failures & at least six good-quality embryos transferred in previous cycles in the registered protocol and infertile women with a history of RIF who had failed to achieve clinical pregnancy despite having four good-quality embryos transferred, and were candidates for IVF/ICSI or freeze embryo transfer cycles, aged <40 years with BMI < 30 kg/m2 in manuscript)

  3. Unclear whether fresh or frozen cycles were studied

  4. Although according to the protocol women with uterine abnormalities were excluded, the analysis performed incorporates patients with Asherman’s syndrome

  5. No flow diagram

  6. No description of the method of randomization

  7. Pregnancy rates reported do not match with the number of pregnancies reported

Evaluation of the effect of intrauterine injection of PRP on the pregnancy rate of patients with a history of implantation failure in the IVF cycle
  1. No information regarding patient enrolment and allocation

  2. No flow chart is present

The effects of autologous PRP in repeated implantation failure: a RCT
  1. Discrepancy in population characteristics in inclusion criteria between the registered protocol and the published manuscript (female age below 40 years is an additional inclusion criterion in the published manuscript while patients with thin endometrium that were included in the registered protocol appeared not be included in the published study)

  2. Discrepancy regarding randomization method between the registered protocol and the published manuscript (registered as a single center, RCT with balanced randomization but published study reported ‘Randomization was carried out using computer-generated simple random tables in a 1:1 ratio’.)

  3. Unclear protocol used regarding the use of sham catheter

PRP in RIF, hope or hype? A prospective randomized controlled study
  1. Retrospective registration of the study

  2. No information regarding the method of randomization used, patient allocation, enrollment, and statistical analysis

Effect of PRP on pregnancy outcomes in infertile women with RIF: a RCT
  1. The study was registered as not-blinded but published as blinded

  2. The number patients lost to follow up is significantly different between the two groups compared

  3. Women above 40 years of age and those with BMI > 30 were excluded as per protocol of the study but shown in the flow chart and included in the intention-to-treat analysis

Intrauterine infusion of autologous PRP before frozen embryo transfer in patients with prior implantation failure: a randomized controlled study
  1. Although the study evaluated women with RIF more than 50% of the patients (55/110) had only a single embryo transfer failure

Autologous intrauterine PRP instillation in repeated implantation failure in assisted reproductive techniques.
  1. No registration ID

  2. Discrepancy regarding the number of previous failed attempts between the registered protocol and the published manuscript

  3. Unclear inclusion criteria

Efficacy of the intrauterine infusion of PRP on pregnancy outcomes in patients with repeated implantation failure: a randomized control trial
  1. No registration ID

  2. No adequate information regarding the randomization method used

The effects of autologous PRP on pregnancy outcomes in repeated implantation failure patients undergoing frozen embryo transfer: a RCT
  1. Same registration ID with the study by Nazari et al. (2019)

  2. Unclear protocol used regarding the use of sham catheter

  3. No information regarding patient allocation and concealment

EMT, endometrial thickness; ID, identity document; ITT, intention-to-treat; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure.

Additionally, using the Cochrane risk-of-bias tool for randomized trials (RoB 2), it was determined that all RCTs were deemed to have an overall high risk of bias, based on the assessment of the domains of the randomization process, deviations from the intended interventions, missing outcome data, measurement of the outcome, and selection of the reported outcome (Supplementary Figs S1 and S2, Supplementary Data File S1). A detailed methodological perusal of the available RCTs is presented in Table 3 and Supplementary Table S2.

Authors of this article attempted to seek clarification from every study but no reply was received in any instance.

Can the meta-analyses overcome quality problems of untrustworthy RCTs?

The meta-analytical synthesis of studies that are at risk of bias does not mitigate the inherent bias of individual studies and may be seriously misleading. If bias is present in each (or some) of the individual studies, meta-analysis will simply compound the errors and produce a ‘wrong’ result that may be interpreted as having more credibility (Higgins et al., 2024).

Therefore, the meta-analyses of RCTs evaluating the role intrauterine PRP infusion in RIF patients may not be trustworthy due to significant biases in the included studies in several areas, such as randomization, adherence to interventions, and outcome reporting, as determined by tools like RoB 2 and the TRACT Screening Checklist.

A systematic review should always evaluate risk of bias and integrity concerns during the review process, exclude studies at significant risk, downgrade evidence if risk of bias is present, and restrict the primary analysis to trials of high quality (Vaidakis et al., 2024) (Table 1).

Are the available RCTs examining the same intervention?

The lack of uniformity in intrauterine autologous PRP infusion protocols in the RCTs published thus far, regarding differences in PRP concentration, volume, frequency of administration, and preparation techniques, hinders the ability to establish consistent and reproducible treatment methods and renders problematic the comparison of outcomes across different studies (Table 4).

Table 4.

Intrauterine autologous PRP infusion protocols used in the available RCTs in patients with RIF.

Study, year, JournalPRP administration
Adverse effects
Method of preparationRouteDose/mode of administrationTime
35 ml of autologous venous blood coated with 5 cc of acid citrate as the anticoagulant solution and centrifuged at 1700g for 12 min. Finally, the separated plasma was centrifuged for 7 min at 3300g.Not reported0.5 ml/once48 h before ETNot reported
10–20 ml of autologous venous blood was drawn into a syringe that contained 2.5 ml of acid citrate anticoagulant solution and centrifuged at 1500 rpm for 10 min. The obtained plasma was then centrifuged at 3000 rpm for 5 min to extract the PRP.*IUI catheter0.5 ml/onceAfter oocyte retrievalNot reported
PRP was taken from the participant’s autologous venous blood simultaneously, then prepared by centrifugal platelets and growth factors isolated and concentrated from the participant’s serum.Not reported0.5–1 ml/once or twice per cycle48 h before ETNone
8.5 ml of autologous venous blood was drawn from the syringe pre-filled with 1.5 ml of anticoagulant solution and centrifuged immediately at 12 000g for 10 min. The plasma layer was collected to another tube and re-centrifuged at 12 000g for 10 min.Not reported1.5 ml/PRP (1.5 ml) was re-injected for two patients who did not have an appropriate endometrial thickness 48 h after the first injection48 h before ETNot reported
8.5 cc autologous venous blood was taken, 2.5 cc acid citrate was added and was centrifugated at 1400 rpm for 10 min. The upper plasma was separated and re-centrifugated at 3500 rpm for 6 min to obtain the PRP.*IUI catheter0.5 cc48 h before ETNone
8 ml of autologous venous blood was taken in a syringe containing 2.5 ml of citrate acid, separated at 1200 rpm for 12 min. Then plasma was reabsorbed at 3300 rpm for 7 min to obtain the PRP.*IUI catheter0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a syringe containing 1.5 ml of acid citrate and centrifuged at 1200 rpm for 10 min to separate the red blood cells. The solution was centrifuged again at 3300 rpm for 5 min to separate plasma and obtain the PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drawn into a syringe containing 2.5 ml of acid citrate and centrifuged at 1200 rpm for 12 min to separate red blood cells, then plasma was centrifuged again at 3300 rpm for 7 min to obtain PRP.*ET catheter0.5–1 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drained into a syringe containing 2.5 ml of acid citrate and anticoagulant solution and centrifuged at 1200 rpm for 12 min to detach red blood cells, and then, plasma was centrifuged for a second time at 3300 rpm for 7 min.*IUI catheter0.5 ml48 h before ET
  • Not reported

15cc of autologous venous blood was collected in specified tubes for PRP at a temperature between 21 and 24°C and first centrifugation was performed at 1200 rpm for 12 min. The upper layer was transferred into another sterile tube and second centrifugation at 3300 rpm for 7 min was done. The upper 2/3 of the tube is discarded while the remaining 1/3 was homogenized and a total of 1 ml of PRP was obtained.*ET catheter under US guidance1 mlOn Day 11 of menstrual cycle and may be repeated on Day 13 if endometrial thickness is still <7 mmNot reported
A syringe with an anticoagulant was used to draw a sample of the autologous venous blood of the patient (10 cm3). PRP was obtained via sequential centrifugation (soft spin 200g/15 min, then hard spin 600g/6 min)IUI catheter under US guidance
  • 0.5–0.8 ml

  • Second sitting of PRP infusion will be performed in a few patients who fail to show desired results after 72 h

72 h before ET in patients with endometrial thickness of 7 mm or moreNone
8.5 ml of autologous venous blood was drawn from the 10-ml syringe pre-filled with 1.5 ml of acid citrate as an anticoagulant solution and was centrifuged at 1600 rpm for 10 min to separate red blood cells. Then, plasma was re-centrifuged at 3500 rpm for 6 min at room temperature (18°C) to obtain 1.5 ml lympho PRP*IUI catheter under US guidance0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a tube containing 1.5 ml of anticoagulant solution and centrifuged at 1200 rpm for 12 min to separate red blood cells. In second step, the harvested plasma was centrifuged at 3300 rpm for 5 min to acquire PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
Study, year, JournalPRP administration
Adverse effects
Method of preparationRouteDose/mode of administrationTime
35 ml of autologous venous blood coated with 5 cc of acid citrate as the anticoagulant solution and centrifuged at 1700g for 12 min. Finally, the separated plasma was centrifuged for 7 min at 3300g.Not reported0.5 ml/once48 h before ETNot reported
10–20 ml of autologous venous blood was drawn into a syringe that contained 2.5 ml of acid citrate anticoagulant solution and centrifuged at 1500 rpm for 10 min. The obtained plasma was then centrifuged at 3000 rpm for 5 min to extract the PRP.*IUI catheter0.5 ml/onceAfter oocyte retrievalNot reported
PRP was taken from the participant’s autologous venous blood simultaneously, then prepared by centrifugal platelets and growth factors isolated and concentrated from the participant’s serum.Not reported0.5–1 ml/once or twice per cycle48 h before ETNone
8.5 ml of autologous venous blood was drawn from the syringe pre-filled with 1.5 ml of anticoagulant solution and centrifuged immediately at 12 000g for 10 min. The plasma layer was collected to another tube and re-centrifuged at 12 000g for 10 min.Not reported1.5 ml/PRP (1.5 ml) was re-injected for two patients who did not have an appropriate endometrial thickness 48 h after the first injection48 h before ETNot reported
8.5 cc autologous venous blood was taken, 2.5 cc acid citrate was added and was centrifugated at 1400 rpm for 10 min. The upper plasma was separated and re-centrifugated at 3500 rpm for 6 min to obtain the PRP.*IUI catheter0.5 cc48 h before ETNone
8 ml of autologous venous blood was taken in a syringe containing 2.5 ml of citrate acid, separated at 1200 rpm for 12 min. Then plasma was reabsorbed at 3300 rpm for 7 min to obtain the PRP.*IUI catheter0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a syringe containing 1.5 ml of acid citrate and centrifuged at 1200 rpm for 10 min to separate the red blood cells. The solution was centrifuged again at 3300 rpm for 5 min to separate plasma and obtain the PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drawn into a syringe containing 2.5 ml of acid citrate and centrifuged at 1200 rpm for 12 min to separate red blood cells, then plasma was centrifuged again at 3300 rpm for 7 min to obtain PRP.*ET catheter0.5–1 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drained into a syringe containing 2.5 ml of acid citrate and anticoagulant solution and centrifuged at 1200 rpm for 12 min to detach red blood cells, and then, plasma was centrifuged for a second time at 3300 rpm for 7 min.*IUI catheter0.5 ml48 h before ET
  • Not reported

15cc of autologous venous blood was collected in specified tubes for PRP at a temperature between 21 and 24°C and first centrifugation was performed at 1200 rpm for 12 min. The upper layer was transferred into another sterile tube and second centrifugation at 3300 rpm for 7 min was done. The upper 2/3 of the tube is discarded while the remaining 1/3 was homogenized and a total of 1 ml of PRP was obtained.*ET catheter under US guidance1 mlOn Day 11 of menstrual cycle and may be repeated on Day 13 if endometrial thickness is still <7 mmNot reported
A syringe with an anticoagulant was used to draw a sample of the autologous venous blood of the patient (10 cm3). PRP was obtained via sequential centrifugation (soft spin 200g/15 min, then hard spin 600g/6 min)IUI catheter under US guidance
  • 0.5–0.8 ml

  • Second sitting of PRP infusion will be performed in a few patients who fail to show desired results after 72 h

72 h before ET in patients with endometrial thickness of 7 mm or moreNone
8.5 ml of autologous venous blood was drawn from the 10-ml syringe pre-filled with 1.5 ml of acid citrate as an anticoagulant solution and was centrifuged at 1600 rpm for 10 min to separate red blood cells. Then, plasma was re-centrifuged at 3500 rpm for 6 min at room temperature (18°C) to obtain 1.5 ml lympho PRP*IUI catheter under US guidance0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a tube containing 1.5 ml of anticoagulant solution and centrifuged at 1200 rpm for 12 min to separate red blood cells. In second step, the harvested plasma was centrifuged at 3300 rpm for 5 min to acquire PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported

ET, embryo transfer; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure; US, ultrasound.

*

Centrifugal diameters are not stated in the published RCT(s) and therefore g cannot be calculated.

Table 4.

Intrauterine autologous PRP infusion protocols used in the available RCTs in patients with RIF.

Study, year, JournalPRP administration
Adverse effects
Method of preparationRouteDose/mode of administrationTime
35 ml of autologous venous blood coated with 5 cc of acid citrate as the anticoagulant solution and centrifuged at 1700g for 12 min. Finally, the separated plasma was centrifuged for 7 min at 3300g.Not reported0.5 ml/once48 h before ETNot reported
10–20 ml of autologous venous blood was drawn into a syringe that contained 2.5 ml of acid citrate anticoagulant solution and centrifuged at 1500 rpm for 10 min. The obtained plasma was then centrifuged at 3000 rpm for 5 min to extract the PRP.*IUI catheter0.5 ml/onceAfter oocyte retrievalNot reported
PRP was taken from the participant’s autologous venous blood simultaneously, then prepared by centrifugal platelets and growth factors isolated and concentrated from the participant’s serum.Not reported0.5–1 ml/once or twice per cycle48 h before ETNone
8.5 ml of autologous venous blood was drawn from the syringe pre-filled with 1.5 ml of anticoagulant solution and centrifuged immediately at 12 000g for 10 min. The plasma layer was collected to another tube and re-centrifuged at 12 000g for 10 min.Not reported1.5 ml/PRP (1.5 ml) was re-injected for two patients who did not have an appropriate endometrial thickness 48 h after the first injection48 h before ETNot reported
8.5 cc autologous venous blood was taken, 2.5 cc acid citrate was added and was centrifugated at 1400 rpm for 10 min. The upper plasma was separated and re-centrifugated at 3500 rpm for 6 min to obtain the PRP.*IUI catheter0.5 cc48 h before ETNone
8 ml of autologous venous blood was taken in a syringe containing 2.5 ml of citrate acid, separated at 1200 rpm for 12 min. Then plasma was reabsorbed at 3300 rpm for 7 min to obtain the PRP.*IUI catheter0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a syringe containing 1.5 ml of acid citrate and centrifuged at 1200 rpm for 10 min to separate the red blood cells. The solution was centrifuged again at 3300 rpm for 5 min to separate plasma and obtain the PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drawn into a syringe containing 2.5 ml of acid citrate and centrifuged at 1200 rpm for 12 min to separate red blood cells, then plasma was centrifuged again at 3300 rpm for 7 min to obtain PRP.*ET catheter0.5–1 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drained into a syringe containing 2.5 ml of acid citrate and anticoagulant solution and centrifuged at 1200 rpm for 12 min to detach red blood cells, and then, plasma was centrifuged for a second time at 3300 rpm for 7 min.*IUI catheter0.5 ml48 h before ET
  • Not reported

15cc of autologous venous blood was collected in specified tubes for PRP at a temperature between 21 and 24°C and first centrifugation was performed at 1200 rpm for 12 min. The upper layer was transferred into another sterile tube and second centrifugation at 3300 rpm for 7 min was done. The upper 2/3 of the tube is discarded while the remaining 1/3 was homogenized and a total of 1 ml of PRP was obtained.*ET catheter under US guidance1 mlOn Day 11 of menstrual cycle and may be repeated on Day 13 if endometrial thickness is still <7 mmNot reported
A syringe with an anticoagulant was used to draw a sample of the autologous venous blood of the patient (10 cm3). PRP was obtained via sequential centrifugation (soft spin 200g/15 min, then hard spin 600g/6 min)IUI catheter under US guidance
  • 0.5–0.8 ml

  • Second sitting of PRP infusion will be performed in a few patients who fail to show desired results after 72 h

72 h before ET in patients with endometrial thickness of 7 mm or moreNone
8.5 ml of autologous venous blood was drawn from the 10-ml syringe pre-filled with 1.5 ml of acid citrate as an anticoagulant solution and was centrifuged at 1600 rpm for 10 min to separate red blood cells. Then, plasma was re-centrifuged at 3500 rpm for 6 min at room temperature (18°C) to obtain 1.5 ml lympho PRP*IUI catheter under US guidance0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a tube containing 1.5 ml of anticoagulant solution and centrifuged at 1200 rpm for 12 min to separate red blood cells. In second step, the harvested plasma was centrifuged at 3300 rpm for 5 min to acquire PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
Study, year, JournalPRP administration
Adverse effects
Method of preparationRouteDose/mode of administrationTime
35 ml of autologous venous blood coated with 5 cc of acid citrate as the anticoagulant solution and centrifuged at 1700g for 12 min. Finally, the separated plasma was centrifuged for 7 min at 3300g.Not reported0.5 ml/once48 h before ETNot reported
10–20 ml of autologous venous blood was drawn into a syringe that contained 2.5 ml of acid citrate anticoagulant solution and centrifuged at 1500 rpm for 10 min. The obtained plasma was then centrifuged at 3000 rpm for 5 min to extract the PRP.*IUI catheter0.5 ml/onceAfter oocyte retrievalNot reported
PRP was taken from the participant’s autologous venous blood simultaneously, then prepared by centrifugal platelets and growth factors isolated and concentrated from the participant’s serum.Not reported0.5–1 ml/once or twice per cycle48 h before ETNone
8.5 ml of autologous venous blood was drawn from the syringe pre-filled with 1.5 ml of anticoagulant solution and centrifuged immediately at 12 000g for 10 min. The plasma layer was collected to another tube and re-centrifuged at 12 000g for 10 min.Not reported1.5 ml/PRP (1.5 ml) was re-injected for two patients who did not have an appropriate endometrial thickness 48 h after the first injection48 h before ETNot reported
8.5 cc autologous venous blood was taken, 2.5 cc acid citrate was added and was centrifugated at 1400 rpm for 10 min. The upper plasma was separated and re-centrifugated at 3500 rpm for 6 min to obtain the PRP.*IUI catheter0.5 cc48 h before ETNone
8 ml of autologous venous blood was taken in a syringe containing 2.5 ml of citrate acid, separated at 1200 rpm for 12 min. Then plasma was reabsorbed at 3300 rpm for 7 min to obtain the PRP.*IUI catheter0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a syringe containing 1.5 ml of acid citrate and centrifuged at 1200 rpm for 10 min to separate the red blood cells. The solution was centrifuged again at 3300 rpm for 5 min to separate plasma and obtain the PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drawn into a syringe containing 2.5 ml of acid citrate and centrifuged at 1200 rpm for 12 min to separate red blood cells, then plasma was centrifuged again at 3300 rpm for 7 min to obtain PRP.*ET catheter0.5–1 ml48 h before ETNot reported
17.5 ml of autologous venous blood was drained into a syringe containing 2.5 ml of acid citrate and anticoagulant solution and centrifuged at 1200 rpm for 12 min to detach red blood cells, and then, plasma was centrifuged for a second time at 3300 rpm for 7 min.*IUI catheter0.5 ml48 h before ET
  • Not reported

15cc of autologous venous blood was collected in specified tubes for PRP at a temperature between 21 and 24°C and first centrifugation was performed at 1200 rpm for 12 min. The upper layer was transferred into another sterile tube and second centrifugation at 3300 rpm for 7 min was done. The upper 2/3 of the tube is discarded while the remaining 1/3 was homogenized and a total of 1 ml of PRP was obtained.*ET catheter under US guidance1 mlOn Day 11 of menstrual cycle and may be repeated on Day 13 if endometrial thickness is still <7 mmNot reported
A syringe with an anticoagulant was used to draw a sample of the autologous venous blood of the patient (10 cm3). PRP was obtained via sequential centrifugation (soft spin 200g/15 min, then hard spin 600g/6 min)IUI catheter under US guidance
  • 0.5–0.8 ml

  • Second sitting of PRP infusion will be performed in a few patients who fail to show desired results after 72 h

72 h before ET in patients with endometrial thickness of 7 mm or moreNone
8.5 ml of autologous venous blood was drawn from the 10-ml syringe pre-filled with 1.5 ml of acid citrate as an anticoagulant solution and was centrifuged at 1600 rpm for 10 min to separate red blood cells. Then, plasma was re-centrifuged at 3500 rpm for 6 min at room temperature (18°C) to obtain 1.5 ml lympho PRP*IUI catheter under US guidance0.5 ml48 h before ETNot reported
8.5 ml of autologous venous blood was drawn in a tube containing 1.5 ml of anticoagulant solution and centrifuged at 1200 rpm for 12 min to separate red blood cells. In second step, the harvested plasma was centrifuged at 3300 rpm for 5 min to acquire PRP.*ET catheter under US guidance0.5 ml48 h before ETNot reported

ET, embryo transfer; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure; US, ultrasound.

*

Centrifugal diameters are not stated in the published RCT(s) and therefore g cannot be calculated.

Are the available RCTs examining a clinically similar population?

Different definitions of RIF have been used in the published RCTs; in 3 out of the 13 RCTs, no definition of RIF was reported (Table 5). As a result, considerable heterogeneity is present in the populations studied regarding the number of unsuccessful embryo transfers, the total number of embryos transferred and female age.

Table 5.

Characteristics of the population studied in the RCTs evaluating intrauterine infusion of autologous PRP.

Study, year, JournalDefinition of RIFPopulation age (years)Subgroup analysis by ageNumber of failed ETsEmbryo euploidyESHRE criteria*  met/not met
Not reportedNot reportedNo1–2UnknownNot met
Not reported18–44No≥1UnknownNot met
Not reported18–45No≥1UnknownNot met
Infertile women with at least two IVF failures≤41No≥2UnknownNot met
Failure to achieve clinical pregnancy despite having four good-quality embryos transferred≤40No≥2UnknownNot met
History of two to three IVF failures≤40No2–3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos≤40No1–10UnknownNot met
History of failed previous ETs attempts between 3 and 5 times≤40No3–5UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos (four embryos) in women aged <40 years20–35No1–4UnknownNot met
≥3 unsuccessful IVF-ETs cycles18–35No2–5UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos and had at least one frozen good-quality blastocyst-stage embryo20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos18–38No≥3UnknownNot met
Study, year, JournalDefinition of RIFPopulation age (years)Subgroup analysis by ageNumber of failed ETsEmbryo euploidyESHRE criteria*  met/not met
Not reportedNot reportedNo1–2UnknownNot met
Not reported18–44No≥1UnknownNot met
Not reported18–45No≥1UnknownNot met
Infertile women with at least two IVF failures≤41No≥2UnknownNot met
Failure to achieve clinical pregnancy despite having four good-quality embryos transferred≤40No≥2UnknownNot met
History of two to three IVF failures≤40No2–3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos≤40No1–10UnknownNot met
History of failed previous ETs attempts between 3 and 5 times≤40No3–5UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos (four embryos) in women aged <40 years20–35No1–4UnknownNot met
≥3 unsuccessful IVF-ETs cycles18–35No2–5UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos and had at least one frozen good-quality blastocyst-stage embryo20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos18–38No≥3UnknownNot met

ESHRE, European Society of Human Reproduction and Embryology; ET, embryo transfer; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure.

*

ESHRE criteria; when embryos of unknown euploidy are transferred, RIF is defined as the presence of three unsuccessful ETs in women under 35 years of age, four unsuccessful ETs in women aged between 35 and 39 years, or six unsuccessful ETs in women aged 40 years and above. When euploid embryos are transferred, RIF is defined as the presence of two unsuccessful ETs regardless of woman’s age (Cimadomo et al., 2023).

Table 5.

Characteristics of the population studied in the RCTs evaluating intrauterine infusion of autologous PRP.

Study, year, JournalDefinition of RIFPopulation age (years)Subgroup analysis by ageNumber of failed ETsEmbryo euploidyESHRE criteria*  met/not met
Not reportedNot reportedNo1–2UnknownNot met
Not reported18–44No≥1UnknownNot met
Not reported18–45No≥1UnknownNot met
Infertile women with at least two IVF failures≤41No≥2UnknownNot met
Failure to achieve clinical pregnancy despite having four good-quality embryos transferred≤40No≥2UnknownNot met
History of two to three IVF failures≤40No2–3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos≤40No1–10UnknownNot met
History of failed previous ETs attempts between 3 and 5 times≤40No3–5UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos (four embryos) in women aged <40 years20–35No1–4UnknownNot met
≥3 unsuccessful IVF-ETs cycles18–35No2–5UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos and had at least one frozen good-quality blastocyst-stage embryo20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos18–38No≥3UnknownNot met
Study, year, JournalDefinition of RIFPopulation age (years)Subgroup analysis by ageNumber of failed ETsEmbryo euploidyESHRE criteria*  met/not met
Not reportedNot reportedNo1–2UnknownNot met
Not reported18–44No≥1UnknownNot met
Not reported18–45No≥1UnknownNot met
Infertile women with at least two IVF failures≤41No≥2UnknownNot met
Failure to achieve clinical pregnancy despite having four good-quality embryos transferred≤40No≥2UnknownNot met
History of two to three IVF failures≤40No2–3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos≤40No1–10UnknownNot met
History of failed previous ETs attempts between 3 and 5 times≤40No3–5UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with good-quality embryos (four embryos) in women aged <40 years20–35No1–4UnknownNot met
≥3 unsuccessful IVF-ETs cycles18–35No2–5UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos and had at least one frozen good-quality blastocyst-stage embryo20–40No≥3UnknownNot met
Failure to conceive after ≥3 ETs with high-quality embryos18–38No≥3UnknownNot met

ESHRE, European Society of Human Reproduction and Embryology; ET, embryo transfer; PRP, platelet-rich plasma; RCTs, randomized controlled trials; RIF, recurrent implantation failure.

*

ESHRE criteria; when embryos of unknown euploidy are transferred, RIF is defined as the presence of three unsuccessful ETs in women under 35 years of age, four unsuccessful ETs in women aged between 35 and 39 years, or six unsuccessful ETs in women aged 40 years and above. When euploid embryos are transferred, RIF is defined as the presence of two unsuccessful ETs regardless of woman’s age (Cimadomo et al., 2023).

This inconsistency in the definition of RIF between studies, or its lack thereof, renders the comparison of outcomes, such as biochemical pregnancy, clinical pregnancy, or live births problematic and limits the generalizability of the results obtained as there is no clear reference population to which the produced effects might be applicable. In such cases, a meta-analysis may be meaningless (mixing ‘apples and oranges’), and genuine differences in effects may be masked or spuriously detected (Higgins et al., 2024). On the other hand, if the raw data of these RCTs were analyzed in an individual participant data meta-analysis, additional insights could be provided regarding the effectiveness of autologous intrauterine PRP infusion.

To address this problem, a uniform definition of RIF has recently been the focus of interest (Kolibianakis and Venetis, 2019; Ata et al., 2021; Cimadomo et al., 2023). In this respect, ESHRE has provided clear guidelines for defining RIF, taking into consideration the euploid status of the embryos transferred directly or indirectly by adjusting the number of failed attempts according to female age (Cimadomo et al., 2023). These criteria are essential for standardizing research in RIF, ensuring that future study results are robust and comparable.

Are the available RCTs examining a real RIF population?

In order for the results of any RCT to be credible, the intervention tested needs to have a high likelihood of biological plausibility, i.e. the RCTs should be testing an intervention in a population that is likely to benefit from this intervention. In this regard, it is important to assess whether the population examined in each RCT evaluating intrauterine PRP infusion truly satisfies the basic criteria to be considered an RIF population. In this respect, the methodology and RIF threshold proposed by ESHRE can identify a population with a real clinical problem that needs to be solved.

Although the ESHRE RIF definition has been published after the majority of the studies evaluating intrauterine infusion of PRP in RIF patients were performed, it is feasible to confirm whether the population of a specific study meets, or not, the ESHRE definition for RIF.

Currently, none of the RIF definitions used in the relevant published RCTs, evaluating the intrauterine infusion of autologous PRP, meet the minimum criteria for RIF proposed by ESHRE (Table 5). In 2 out of the 13 RCTs (Dawood, 2022; El-Samman et al., 2022), patients evaluated were <35 years of age; however, in these studies, patients with less than three failed ETs were included, thus not complying with ESHRE’s definition of RIF for this age group (three or more failed ETs).

As a consequence, intrauterine infusion of autologous PRP in these RCTs is applied to patients who do not fulfill the ESHRE criteria for RIF and therefore do not examine a real RIF population, according to ESHRE (Cimadomo et al., 2023).

Is clinical use of intrauterine infusion of autologous PRP justified in RIF patients?

Given the absence of RCTs in women with RIF, as recently proposed by ESHRE, no evidence currently exists to accept or refute a beneficial role of intrauterine infusion of autologous PRP on the probability of pregnancy in these patients. Consequently, its clinical use cannot be currently recommended and further research is needed to assess its role in patients with RIF.

How can future research evaluating intrauterine infusion of autologous PRP in RIF patients meaningfully guide clinical practice?

Future RCTs should be designed with strict adherence to the ESHRE criteria of RIF so that they are able to evaluate a homogeneous population of patients with a real clinical problem. Furthermore, future research should aim to identify the optimal methods for preparing and administering PRP. In this way, the resulting data can be meaningfully synthesized, leading to robust evidence on which clinicians can rely when making treatment decisions for RIF patients.

The potential of intrauterine infusion of autologous PRP to improve outcomes for women with RIF remains an important area of research in assisted reproductive technologies. However, the current evidence is insufficient to inform clinical practice, highlighting the need for well-designed studies to provide clearer guidance.

Data availability

The data underlying this article are available in the article and in its online supplementary material.

Authors’ roles

E.T.K.: conceived the idea for the study, contributed to study conception and design, performed the literature search, and contributed toward the data extraction, the analyses and interpretation of the data, and the drafting of the manuscript. E.M.K.: constructed the protocol and contributed toward the data extraction, the analyses and interpretation of the data, and the drafting of the manuscript. C.A.V.: reviewed the protocol, contributed toward the literature search, interpretation of the data, and revised the manuscript for important intellectual content. J.K.B.: reviewed the protocol and revised the manuscript for important intellectual content. All authors approved the final version of the manuscript.

Funding

No financial support was received for this study.

Conflict of interest

No conflicts of interest were declared on behalf of E.T.K., J.K.B., and C.A.V. E.M.K. has declared the following conflicts of interest: payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events from Ferring, Vianex, IBSA, and Merck Serono and support for attending meetings and/or travel from Merck Serono.

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