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SneakPeek Early Gender Test: The Earliest and Most Accurate Method for Fetal Sex Determination at 6-Weeks Gestation

Henriett Diana Szucs*, Lia Asprer, Nora Abunadi, Haley Milot, Sarah Cacia, Chris Jacob

Background: The SneakPeek® Early Gender Test was previously shown to be 99.9% accurate in determining fetal sex as early as seven weeks of gestation. To our knowledge, no prior study has shown fetal sex identification from maternal plasma earlier than seven weeks of gestation with high accuracy. The SneakPeek assay was further optimized to enable fetal sex identification at earlier gestations and its performance characteristics were determined at 6-weeks’ gestation.

Method: Between May and September 2021, 156 pregnant women were recruited from 12 clinics in the United States. After excluding participants that reported miscarriage during the study, reported twin/triplet pregnancy, or miscalculated gestational age at the time of the initial sample collection, 115 individuals completed the trial in its entirety. Three to four milliliters (mL) of maternal blood were drawn from each participant via venipuncture at three gestational ages (i.e., 6, 7, and 8 - 10 weeks’ gestation). Maternal plasma was separated from whole blood via centrifugation. Using a commercial DNA isolation kit, circulating cell-free DNA (ccfDNA) was extracted from the maternal plasma samples. Real-time quantitative PCR was utilized to detect male fetal DNA using a multi-copy sequence on the Y chromosome and total cell-free DNA using an autosomal control target gene. Fetal sex was determined from the qPCR results using an algorithm that includes the Quantification Cycle (Cq) values of the Y-target sequence and autosomal control gene. Since the SneakPeek® Early Gender Test was found to be 99.9% accurate at 7-weeks’ and 8-weeks’ gestation or later, the fetal sex test results for six-week gestation samples were confirmed with the 7-week and 8-week to 10-week sample results. Sonography was also used to confirm SneakPeek test results for 103 pregnancies in the study.

Results: SneakPeek accurately determined fetal sex at six weeks for 113 subjects in this study, results for two subjects were inconclusive. Test results at later gestational ages (7 and 8+ weeks) matched the six-week test results. All sonogram results matched the SneakPeek test results in this study. SneakPeek accuracy, sensitivity, and specificity were 100%, 100%, and 100% for fetal sex identification, respectively. No false positive or false negative results were observed in this study.

Conclusion: SneakPeek® Early Gender Test was shown to be 100% accurate for fetal sex determination at 6 weeks gestation. SneakPeek gender test is the earliest and most accurate method for fetal sex determination. The SneakPeek Early Gender DNA Test can provide prenatal genetic information a month earlier than traditional noninvasive prenatal tests (e.g., NIPS).