Early detection of cell-free fetal DNA in maternal plasma

ObjectivesWe aimed to establish the earliest gestational age at which fetal DNA in maternal plasma could be detected and whether this was reliable at 12–13 weeks' gestation.Study designA prospective observational cohort study of 32 pregnancies either after IVF or before prenatal diagnosis by CVS. Maternal blood was taken and RT-PCR was carried out to detect the multi-copy Y chromosome associated DSY14 gene. The end point was gender as assessed at delivery or on karyotype.ResultsY signal was obtained as early as 14 days post conception (4 weeks' gestation) and has a good prediction rate by 12 weeks' gestation.ConclusionFree fetal DNA allows very early prediction of fetal sex in some cases and could be useful for clinical use for X-linked conditions by the end of the first trimester.