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.