Early Fetal Sex Determination using Cell-Free DNA in Micro-Volume of Maternal Plasma

Abstract

Background: A qPCR-based assay, SneakPeek® Early Gender Test (Gateway Genomics), has been developed to determine fetal sex as early as 9 weeks gestation using a micro-volume of maternal plasma. The purpose of this study was to assess the clinical performance of SneakPeek for noninvasive prenatal testing (NIPT) of fetal sex. Methods: A multicenter blinded study was conducted at fourteen ultrasound clinics with maternal blood samples collected from 241 pregnant women between 8.43 and 36.86 weeks of gestation. Plasma was separated from whole blood by double-centrifugation. Circulating cell-free DNA was isolated from a micro-volume of maternal plasma (100 μL) using a commercial DNA extraction kit (NucleoSpin® Plasma XS, Macherey-Nagel). Real-time quantitative PCR was performed to detect fetal DNA using a multi-copy sequence on the Y-chromosome. An autosomal control gene was used to measure total cell-free DNA (maternal and fetal cfDNA). Fifty-nine maternal plasma samples were tested twice, on different days, to assess the precision of SneakPeek. Cell-free DNA was detected in all maternal blood samples. Results: Y-chromosome DNA was detected in all samples from women carrying a male fetus. Sneak Peek correctly identified fetal sex in 240 of the 241 samples. Fetal sex for all samples was unknown prior to genetic testing and was confirmed via sonographic evaluation at the conclusion of the study. SneakPeek accuracy, sensitivity and specificity were 99.6%, 100% and 99.1% for fetal sex identification, respectively. Conclusion: This blinded multicenter study showed that SneakPeek Early Gender Test is highly accurate for fetal sex determination in early pregnancy. This micro volume noninvasive prenatal test for early fetal sex determination could simplify the collection of maternal blood and increase the accessibility of NIPT to a broad population.