Non‐invasive prenatal testing in the management of twin pregnancies

• Published in: Prenatal diagnosis Vol. 41; no. 10; pp. 1233 - 1240
• Main Authors: Benn, Peter, Rebarber, Andrei
• Format: Journal Article
• Language: English
• Published: Charlottesville Wiley Subscription Services, Inc 01.09.2021; John Wiley and Sons Inc
• Subjects: Aneuploidy; Complications; Deoxyribonucleic acid; DNA; Fetal resorption; Fetuses; Pregnancy; Pregnancy complications; Review; Screening; Twins; Ultrasonic imaging; Ultrasound; Zygosity
• ISSN: 0197-3851; 1097-0223
• DOI: 10.1002/pd.5989

Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta‐analyses show that non‐invasive prenatal testing (NIPT) through analysis of cell‐free DNA (cf‐DNA) is superior to serum and ultrasound‐based tests. The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT. Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf‐DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf‐DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies. Key Points What's already known about this topic? In singleton pregnancies, non‐invasive prenatal testing (NIPT) for fetal aneuploidy is more effective than conventional serum and ultrasound‐based screening tests. NIPT is more complex in dizygotic twin pregnancies due to the presence of two fetal genotypes. Overall fetal fraction is higher in twin pregnancies but the individual contribution for each fetus is lower. What does this study add? A review of cell‐free DNA testing in twin pregnancies. Individual fetal fractions in dizygotic twin pregnancies can be measured. Zygosity can be established using NIPT and this can be particularly useful when there are concerns about chorionicity or determining whether one versus two fetuses are affected. Vanishing twins can be detected through NIPT and this testing could be considered for some apparently singleton pregnancies with complications.