Quantitative variation analysis of fetal DNA in maternal plasma samples collected before and after amniocentesis.

Aims: The aim of this study was to evaluate possible procedure-related variations in the levels of cell-free fetal DNA (fDNA) in maternal plasma of women undergoing genetic amniocentesis. Materials and Methods: Blood samples were collected at 16–18 weeks’ gestation from 33 pregnant women attending the Fetal Medicine Unit for genetic amniocentesis. For each woman, two blood samples were obtained: the first immediately before amniocentesis and the second one 15 min after the procedure. A real-time quantitative polymerase chain reaction assay, using primers for SRY and beta-globin genes, was used to assess fDNA concentrations in maternal plasma. A Wilcoxon signed-rank test was used for statistical analysis. Results: The karyotype on cultured amniocytes showed that 15 out of 33 women had a male fetus. Real-time quantitative polymerase chain reaction results, on maternal plasma sample pairs from known male pregnancies, showed no significant variations of fDNA correlated to amniocentesis (P = 0.394). Conclusions: Our preliminary study suggests that amniocentesis, although invasive, could be associated with minimal, if any, disruption at the fetal–maternal interface, as revealed by the lack of substantial modifications of fDNA levels in maternal circulation.