First trimester twin discordance as a predictor of adverse twin pregnancy outcomes

Abstract

PREGNANCY OUTCOMES JUDY TAI, WILLIAM GROBMAN, Northwestern University, Department of Obstetrics and Gynecology, Chicago, Illinois OBJECTIVE: To evaluate the association between first-trimester crown rump length (CRL) discordance in twin gestations and subsequent adverse pregnancy outcomes. STUDY DESIGN: Women who received first-trimester ultrasound of twin pregnancies between 7 and 14 weeks of gestation and subsequently delivered between June 2000 and March 2006 at a single tertiary care academic medical center were identified. Maternal and neonatal charts were abstracted for demographic characteristics, ultrasound data, and pregnancy outcomes. The percentage difference in CRL was calculated as the difference in CRL’s divided by the larger CRL. The percentage difference in birth weight (BW) was calculated as the difference in BW’s divided by the larger BW, and if O20% was defined as discordant. RESULTS: One-hundred and seventy eight women met inclusion criteria. The mean CRL difference was 5.9% and the mean BW difference was 11.4%. The CRL difference was significantly correlated with birth weight difference (r =0.43; P!.0001). The 85th percentile for CRL difference in this population was 11.1%. Those women with CRL differences O=85th percentile had a similar maternal age, EGA at time of first trimester scan, and frequency of monochorionicity as those women with twin CRL differences of !85th percentile. However, when the CRL difference was at O=85th percentile, women were more likely to have twins that were discordant at birth (46% vs. 8%, P !.001), be admitted to the NICU (59% vs. 38%, P!.05), and have significant perinatal morbidity (48% vs. 24%, P!.01). CONCLUSION: The CRL difference in the first trimester is correlated with differences in the ultimate BW of twins, and a CRL difference greater than the 85th percentile is associated with several measures of adverse perinatal outcome.