Cross-reactivity with Chlamydia psittaci by microimmunofluorescence assay. Time point 1: test performed upon hospital admission; immunoglobulin M (IgM) and immunoglobulin G (IgG) negative. Time point 2: 4 days after intrauterine fetal death (and 12 days after initial symptoms); IgM not interpretable due to presence of unspecific fluorescence, IgG positive. Positive specific fluorescence: presence of granular fluorescence in the cytoplasm and between the cells (eg, positive control). Unspecific fluorescence: differentiation between unspecific and specific fluorescence by comparison of fluorescence of infected cells to uninfected cells (nonspecific binding control).