title: Vanishing twin as a potential source of bias in non-invasive fetal sex determination: a case report.
abstract: Detection of fetal sex based on fetal DNA present in maternal plasma is already in clinical use. Here we present a case of false positivity during the first trimester which may be attributable to a vanishing twin. The presence of Y-chromosome-specific sequences is used as a marker to indicate a male fetus and the absence of a female fetus. Fetal sex determination was conducted in a pregnant woman at gestational week 10. The sample was positive in all triplicates. Ultrasonography at gestational week 20 revealed female sex. Analysis of sample taken at gestational week 22 indicated a female fetus. According to recently published meta-analyses, non-invasive prenatal diagnosis of fetal sex has high sensitivity and specificity values. Nevertheless, false negative and false positive cases occur. Future studies focusing on the dynamics of fetal DNA are needed. Vanishing twin might be one of the possible causes of false positivity in fetal sex determination.
authors.affiliation: Institute of Molecular Biomedicine, Comenius University, Bratislava, Slovakia.
authors.forename: Barbora
authors.initials: B
authors.lastname: Vlková
authors.forename: Július
authors.initials: J
authors.lastname: Hodosy
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D041322:Chromosomes, Human, Y / Q000378:metabolism*; D004247:DNA / Q000097:blood*; D005189:False Positive Reactions; D005260:Female; D005327:Fetal Resorption / Q000097:blood*; D006801:Humans; D008297:Male; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D059285:Pregnancy, Twin / Q000097:blood*; D012732:Sex Determination Analysis; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004247:DNA
keywords: cell-free fetal DNA; fetal sex; prenatal diagnostics; vanishing twin syndrome