![]() 12, 14 Also, it has been estimated that approximately 24% of successful IVF procedures result in multiple gestation, increasing even the risk of monozygotic twins. 12, 13 In Europe and the US for example, the incidence of dizygotic twins corresponded to births, but mainly due to in vitro fertilization (IVF) the incidence is rising to 16– births today. While the incidence of monozygotic twins is about 3– births, the rate of dizygotic twins varies with maternal age, gravidity, ethnicity, familial history, and the use of assisted reproductive techniques. Moreover, the rate of multiple gestation has dramatically increased over the last few years. Since standard sequential screening tests are not very precise in multiple gestation, and considering the increased risks for complications associated with this type of pregnancy, it is important to develop accurate non-invasive methods to identify aneuploidy and sex discordances in twins to improve overall pregnancy management. 10, 11 However, little information is available about the precision of NIPT for fetal sex determination in twins. It has been demonstrated that the performance of NIPT for aneuploidy detection is best achieved in singleton pregnancies when compared to multiple gestation. 8, 9 In both methods, the fetus is presumed to be male or female based on whether Y chromosome material is detected or not. 6, 7Ĭurrently, prediction of fetal sex in NIPT is performed using either real-time PCR or Y chromosome read counting. 5 It is noteworthy mentioning that the assessment of fetal sex through NIPT offers earlier test results compared to ultrasound, and has been shown to reduce the number of invasive procedures significantly. 1 Discrimination of fetal sex is clinically relevant not only for families at high risk of sex-linked disorders, such as hemophilia and Duchenne muscular dystrophy, 2, 3 but also in cases for which the development of external genitalia is ambiguous, 4 and in some endocrine disorders like congenital adrenal hyperplasia, where there is a masculinization of the female fetus that can be preventable with antenatal treatment. Although the main purpose of NIPT is the screening for the viable autosomal aneuploidies (trisomies 21, 18, and 13), the test was first established in clinical setting for fetal sex determination, based on the presence or absence of Y chromosome sequence in the maternal plasma. Non-invasive prenatal testing (NIPT) using cell-free DNA (cfDNA) is changing the standard care in obstetrics. Since sex determination can be clinically important, implementing fetal sex determination in twins will improve overall twin pregnancies management. The model determines fetal sex with 100% sensitivity and specificity when both twins are female, and with 98% sensitivity and 95% specificity when a male is present. A second-step regression analysis was applied when one or both twins were predicted to be male. The prediction was based on a multinomial logistic regression using the normalized frequency of X and Y chromosomes, and fetal fraction estimation. A retrospective analysis was performed using a total of 198 twin pregnancies with documented sex. ![]() Here, we present an accurate sex prediction model to discriminate fetal sex in both dichorionic diamniotic (DCDA) and monochorionic diamniotic/monochorionic monoamniotic (MCDA/MCMA) twin pregnancies. Non-invasive prenatal testing (NIPT) is accurate for fetal sex determination in singleton pregnancies, but its accuracy is not well established in twin pregnancies.
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