Title: 187: Prediction of significant birth weight discordance in twin pregnancies with second and third trimester ultrasound
Abstract: To establish 2nd and 3rd trimester ultrasound predictors of clinically significant intertwin birthweight (BW) discordance (18% as prospectively determined by this group). This prospective cohort study of 1,028 unselected twin pairs recruited over a two year period at 8 academic centers for the Evaluation of Sonographic Predictors of Restricted Growth in Twins (ESPRIT). Participants underwent 2- weekly ultrasonographic surveillance from 24 weeks gestation with surveillance of monochorionic (MC) twins 2-weekly from 16 weeks. Complete biometry was available for 960 twin pairs without TTTS. Biometric data from 20 to 40 weeks were evaluated as predictors of a BW discordance level >18%. Outcomes were adjusted for chorionicity and gestational age using stepwise logistic regression (significance level <0.05) Between 20 and 24 weeks, a BW discordance level > 18% is predicted most accurately by an intertwin discrepancy in biparietal diameter (BPD) > 5%. At 28-32 weeks an intertwin femur length (FL) discordance of 5% or greater is most useful in predicting 18% BW discordance. Late in the third trimester (32-36 weeks) abdominal circumference (AC) of 10% correlates most closely with BW discordance. The greatest sensitivity and specificity of any single predictor is an estimated fetal weight (EFW) discordance > 10% at 32 to 36 weeks. Cumulative analysis of all above sonographic predictors offers the most accurate means of predicting significant BW discordance way (sensitivity 67%, specificity 87%). Sonographic biometry in the 2nd and 3rd trimester can successfully identify twin pregnancies at risk for significant BW discordance. Although these individual parameters are helpful in predicting BW discordance, it is a sequential and cumulative pattern observed on serial evaluation that is most sensitive and specific. Importantly, for all individual biometric measurements and for composite biometry, ultrasound underestimates intertwin size discordanceTabled 1Second and third trimester predictors of significant birthweight discordance of > 18% Open table in a new tab