Maternal urinary cell free fetal DNA in relation to gestational age

Objectives: To evaluate the presence of cell-free fetal DNA in the maternal urine in relation to gestational age as a potential source for non-invasive prenatal diagnosis. Material and methods: One hundred and sixty normal pregnant women were included in the study; 80 women pregnant with male fetuses and 80 women pregnant with female fetuses. Maternal urine of all patients was examined at 12, 16 and 20 wks' gestation for the SRY gene (sex-determining region Y) as a cffDNA (cell free fetal DNA) marker and Ribonuclease P RNA component H1 (RPPH1) as a total cfDNA (cell free DNA) marker using a quantitative real-time PCR assay. Results: SRY gene was detected in maternal urine of those pregnant with male fetuses starting from 16 weeks in 25% (20/80) of cases only and in 80% of cases (64/80) at 20 weeks, but it was not detected at 12 weeks. All women female fetuses were negative for SRY gene. Conclusions: Cell free fetal DNA in maternal urine was not detected in early gestational age using SRY gene alone despite the use of extraction kit specific for extraction of Free-circulating nucleic acids and highly sensitive reported PCR technique. Further studies should be done to evaluate whether cell free fetal DNA in maternal urine can be detected after reaching a certain threshold in blood.