First trimester prediction of growth discordance in twin gestations

Objective The purpose of this study was to determine whether first trimester ultrasound scanning can identify twin gestations that are at risk for subsequent growth discordance. Study design Ultrasound examinations of dichorionic twin pregnancies between 11 and 14 weeks of gestation were evaluated for growth discordance with crown-rump length. Pregnancies that were complicated by fetal death or anomalies were excluded from the analysis. Birth weight discordance was defined as ≥20% difference in birth weight, relative to the larger twin. Fisherʹs exact, Mann Whitney U, and Spearman rho tests were used for statistical analysis. Results Of 130 twin pregnancies, 16 pregnancies (12.3%) had discordant birth weight. Crown-rump length disparity was correlated positively with birth weight discordance (r = 0.31; P<.001). Of pregnancies with a discrepancy of ≤3 days in estimated gestational age, only 9.2% were discordant at birth compared with 45.5% of pregnancies with >3 days discrepancy (P = .004), which resulted in a likelihood ratio of 5.9 for having discordant birth weight. Conclusion Twins who are ultimately discordant at birth may exhibit differences in growth as early as 11 to 14 weeks of gestation.