Indeed, both nuchal translucency abnormalities and crown-rump length discrepancies have been associated with an increased risk of twin-twin Nuchal Translucency Evaluation transfusion syndrome [66-68]. A crown-rump discrepancy of >10% is associated with almost a doubling the risk of developing twin-twin transfusion syndrome [67,68]. Nuchal translucency discordance >20% has been associated with a >30% risk of severe twin-twin transfusion syndrome and early fetal death compared with a <10% risk when the discordance is <20% [69]. As in singletons and dichorionic twins, an increased nuchal translucency in monochorionic twins is associated with fetal aneuploidy, genetic syndromes, structural anomalies, and intrauterine demise. Genetic counseling, invasive diagnostic testing, fetal anatomic surveys, and fetal echocardiography are recommended in monochorionic twin pregnancies complicated by increased nuchal translucency thickness affecting one or both twins. Serial US surveillance of monochorionic twins is advised because of complications associated with sharing a single placenta such as twin-twin transfusion syndrome, unequal placental sharing with discordant twin growth and selective intrauterine growth restriction, and twin anemia polycythemia sequence [64,70]. Because of these unique complications, women with monochorionic pregnancies are followed more closely than dichorionic pregnancies; serial US evaluations every 2 weeks starting at 16 weeks until delivery should be considered [45]. Despite its potential value, a recent review concluded that it is not currently possible to predict adverse outcomes in monochorionic twin pregnancies based on nuchal translucency assessment alone [71].
Nuchal Translucency Evaluation at 11 to 14 Weeks Gestational Age. Indeed, both nuchal translucency abnormalities and crown-rump length discrepancies have been associated with an increased risk of twin-twin Nuchal Translucency Evaluation transfusion syndrome [66-68]. A crown-rump discrepancy of >10% is associated with almost a doubling the risk of developing twin-twin transfusion syndrome [67,68]. Nuchal translucency discordance >20% has been associated with a >30% risk of severe twin-twin transfusion syndrome and early fetal death compared with a <10% risk when the discordance is <20% [69]. As in singletons and dichorionic twins, an increased nuchal translucency in monochorionic twins is associated with fetal aneuploidy, genetic syndromes, structural anomalies, and intrauterine demise. Genetic counseling, invasive diagnostic testing, fetal anatomic surveys, and fetal echocardiography are recommended in monochorionic twin pregnancies complicated by increased nuchal translucency thickness affecting one or both twins. Serial US surveillance of monochorionic twins is advised because of complications associated with sharing a single placenta such as twin-twin transfusion syndrome, unequal placental sharing with discordant twin growth and selective intrauterine growth restriction, and twin anemia polycythemia sequence [64,70]. Because of these unique complications, women with monochorionic pregnancies are followed more closely than dichorionic pregnancies; serial US evaluations every 2 weeks starting at 16 weeks until delivery should be considered [45]. Despite its potential value, a recent review concluded that it is not currently possible to predict adverse outcomes in monochorionic twin pregnancies based on nuchal translucency assessment alone [71].