Vanished Twins and Misdiagnosed Sex: A Case Report with Implications in Prenatal Counseling Using Noninvasive Cell-Free DNA Screening.

Cell-free DNA testing is a recently introduced method for screening pregnant women for fetal trisomy, which is associated with some common significant genetic diseases, as well as the sex of the fetus. The case described here demonstrates the connection between the ultrasound "vanishing twin" phenomenon and the misdiagnosis of prenatal sex using cell-free DNA testing. © Copyright 2016 by the American Board of Family Medicine.