Maternal urine for prenatal diagnosis--an analysis of cell-free fetal DNA in maternal urine and plasma in the third trimester.

Objectives: The aim of the study was the detection, quantification and correlation of cell-free fetal (cff) DNA in maternal urine and plasma in normal and complicated pregnancies during the third trimester.

Methods: One hundred and fifty-one urine and plasma samples obtained from 96 women carrying male fetuses, and 55 carrying female fetuses were collected and analyzed for cff-DNA using fluorescent PCR and quantitative real-time PCR. DNA was extracted from 1 mL maternal urine and analyzed with two different primer sets (SRY and DYS-14). The concentrations of cff and total DNA in maternal plasma were correlated with maternal and obstetric parameters using appropriate correlation analyses.

Results: Y-chromosome-specific sequences were detected in 31 of 96 (32.3%) urine samples collected from women pregnant with male fetuses using DYS-14 and in 6 of 96 (6.3%) urine samples using SRY as primers using real-time PCR. All 96 plasma samples obtained from women carrying male fetuses were positive for cff-DNA using real-time PCR. Cff-DNA exhibited a correlation with gestational age (R = 0.244; P = 0.018) and an inverse correlation with the latency between blood collection and birth (R = - 0.218; P = 0.036). Total DNA showed a correlation with placental weight (R = 0.182; P = 0.034) and pregnancy-associated complications (R = 0.280; P < 0.001).

Conclusion: Our data confirm that cff-DNA is cleared by the kidneys in detectable amounts, but due to its low concentration or problematic detection in maternal urine this source seems inappropriate for noninvasive prenatal diagnosis.