First trimester prediction of growth discordance in twin gestations

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.

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 >or=20% difference in birth weight, relative to the larger twin. Fisher's exact, Mann Whitney U, and Spearman rho tests were used for statistical analysis.

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 discrepancy (P=.004), which resulted in a likelihood ratio of 5.9 for having discordant birth weight.

Twins who are ultimately discordant at birth may exhibit differences in growth as early as 11 to 14 weeks of gestation.