When are amniotic fluid viral PCR studies indicated in prenatal diagnosis?

To determine which prenatal ultrasound findings indicate the need to also obtain PCR studies for viral genome in women undergoing midtrimester amniocentesis.

This was a retrospective observational study on women that underwent amniotic fluid karyotyping and viral PCR testing for history or ultrasound based indication. Amniotic fluid was tested for adenovirus, cytomegalovirus, respiratory syncytial virus, enterovirus, Epstein-Barr virus, and parvovirus B19 using multiplex PCR study with multiple appropriate controls. Ultrasound findings were coded as normal or abnormal with 34 categories of ultrasound abnormality stratified into 18 subgroups. Relationships between these subgroups and karyotype/PCR results were tested by Pearson chi-square method or Fisher's exact test and overall logistic regression analysis.

Amniotic fluid samples from 1191 patients were obtained for the study. Abnormal karyotype was detected in 5.4% of cases (64/1191), and PCR was positive in 6.5% of cases (77/1191). Abnormal fetal ultrasonographic findings were observed in 28.4% of cases (338/1191). There was an association between intrauterine growth restriction, nonimmune hydrops fetalis, hand/foot anomalies or neural tube defects (NTDs), and PCR positivity. NTDs were associated with PCR positivity in fetuses with normal karyotype and nuchal thickening, cardiac or ventral wall defects were specifically associated with aneuploidy.

Amniotic fluid viral PCR testing should be considered for fetuses with intrauterine growth restriction, nonimmune hydrops fetalis, hand/foot anomalies, or NTDs. After aneuploidy is excluded, NTDs are associated with PCR positivity.