Does Early Second‐Trimester Sonography Predict Adverse Perinatal Outcomes in Monochorionic Diamniotic Twin Pregnancies?

Objectives To determine whether intertwin discordant abdominal circumference, femur length, head circumference, and estimated fetal weight sonographic measurements in early second‐trimester monochorionic diamniotic twins predict adverse obstetric and neonatal outcomes. Methods We conducted a multicenter retrospective cohort study involving 9 regional perinatal centers in the United States. We examined the records of all monochorionic diamniotic twin pregnancies with two live fetuses at the 16‐ to 18‐week sonographic examination who had serial follow‐up sonography until delivery. The intertwin discordance in abdominal circumference, femur length, head circumference, and estimated fetal weight was calculated as the difference between the two fetuses, expressed as a percentage of the larger using the 16‐ to 18‐week sonographic measurements. An adverse composite obstetric outcome was defined as the occurrence of 1 or more of the following in either fetus: intrauterine growth restriction, twin‐twin transfusion syndrome, intrauterine fetal death, abnormal growth discordance (≥20% difference), and very preterm birth at or before 28 weeks. An adverse composite neonatal outcome was defined as the occurrence of 1 or more of the following: respiratory distress syndrome, any stage of intraventricular hemorrhage, 5‐minute Apgar score less than 7, necrotizing enterocolitis, culture‐proven early‐onset sepsis, and neonatal death. Receiver operating characteristic and logistic regression–with–generalized estimating equation analyses were constructed. Results Among the 177 monochorionic diamniotic twin pregnancies analyzed, intertwin abdominal circumference and estimated fetal weight discordances were only predictive of adverse composite obstetric outcomes (areas under the curve, 79% and 80%, respectively). Receiver operating characteristic curves showed that intertwin discordances in abdominal circumference, femur length, head circumference, and estimated fetal weight were not acceptable predictors of twin‐twin transfusion syndrome or adverse neonatal outcomes. Conclusions In our cohort, only second‐trimester abdominal circumference and estimated fetal weight discordances in monochorionic diamniotic twin pregnancies were predictive of adverse composite obstetric outcomes. Twin‐twin transfusion syndrome and adverse neonatal outcomes were not predicted by any of the intertwin discordances measured.