Non-invasive fetal sex determination using a conventional nested PCR analysis of fetal DNA in maternal plasma.

Background: In order to provide a reliable non-invasive method for fetal sex determination in a routine setting, we evaluated the possibility of identifying the fetal Y chromosome-specific sequence in maternal plasma using conventional PCR analysis.

Methods: Fetal gender was determined in 31 pregnant women including one with a dizygotic twin pregnancy between 7 and 32 weeks of gestation using DNA extracted from 200 microl of each maternal plasma. The 198 bp SRY gene-specific sequence on Y chromosome and the 261 bp ATL1 gene-specific sequence on X chromosome were co-amplified in a multiplex nested PCR manner. The result was confirmed by routine analysis of fetal tissue obtained by invasive procedure or examination of newborns after delivery.

Results: The 198 bp SRY-specific sequence was detected in 15 plasma samples obtained from pregnant women carrying male fetuses. In the remaining cases bearing female fetuses, only the 261 bp ATL1 gene sequence was detected, producing 100% sensitivity and specificity of fetal sex prediction. The result was completely concordant with the conventional fetal tissue analysis and examination of the newborns after delivery.

Conclusions: A conventional nested PCR analysis of maternal plasma could be used for accurate fetal gender detection and enable a reliable prospective non-invasive fetal sex determination which should enhance prenatal diagnostic options especially for sex-linked disorders.