Chapter 15 - Noninvasive prenatal screening in twin pregnancies

Abstract

Twin pregnancies present a challenge for traditional aneuploidy screening methods, and both first and second trimester screening using maternal serum and/or ultrasound perform less well in twins than in singletons. NIPT offers a more sensitive and specific method to screen for trisomy 21 in twin pregnancies and can in some cases go further and provide more detailed information which may be of particular assistance in twin pregnancy management. The sonographic identification of a twin gestation with discordant findings can present a counselling dilemma. It is likely that with further experience and technological advances, NIPT may be able to provide more precise risk assessment for these pregnancies. Monozygotic twins, although they almost always have identical chromosomes, can rarely be discordant, and here too there are ways in which NIPT may now or in the future be able to help to give further insights. NIPT is not a replacement for diagnostic testing, and irreversible decisions about pregnancy mangagement should not be made based upon NIPT results in isolation. However, NIPT can be a valuable tool in helping the clinician to assess twin pregnancies and has the potential to undergo further technological developments which may help in challenging cases of discordance.