Growth patterns of monochorionic twin pregnancies complicated by type-3 selective fetal growth restriction.

OBJECTIVE

Little is known regarding fetal growth patterns of monochorionic twins complicated by type 3 selective fetal growth restriction (sFGR). We aimed to assess fetal growth and Doppler patterns in type 3 sFGR across gestation and evaluate the effect of changing Doppler flow patterns on growth and intertwin weight discordance.

METHODS

We retrospectively reviewed all type 3 sFGR pregnancies managed at nine fetal centers over a 12-year time period. Higher-order multiples, major fetal anomalies, or other monochorionicity-related complications at initial presentation were excluded. Estimated fetal weights (EFW) for each twin pair in each of five gestational age blocks (16-20, 21-24, 25-28, 29-32 and above 32 weeks' gestation) were reviewed and compared to singleton growth as well as uncomplicated monochorionic twin growth. EFW and intertwin growth discordance were compared between pregnancies with normalization of umbilical artery Dopplers of the smaller twin and those with persistently abnormal Dopplers .

RESULTS

328 pregnancies (656 fetuses) met the study criteria. In type 3 sFGR, the smaller twin was smaller than the average singleton fetus (z-score ranging from -1.52 at 16 weeks to -2.7 at 36 weeks) and the average monochorionic twin (z-score ranging from -1.73 at 16 weeks to -1.49 at 36 weeks), throughout the entire pregnancy, while the larger twin was larger than an average singleton fetus until 22 weeks' gestation and similar in weight to an average monochorionic twin throughout gestation. As pregnancy advanced, both twin's growth velocities decreased with the larger twin remaining appropriately grown and the smaller twin becoming more growth restricted. Intertwin growth discordance remained stable throughout gestation. In multivariable longitudinal modelling, normalization of fetal Dopplers was associated with better growth of the smaller twin (p=0.002) but not the larger twin (p=0.1), without affecting the intertwin growth discordance (p=0.08).

CONCLUSION

Abnormal fetal growth of the smaller twin in type 3 sFGR was evident from early in pregnancy, while the larger twin's growth remained normal throughout gestation. Normalization of Dopplers resulted in improved fetal growth of the smaller twin. This article is protected by copyright. All rights reserved.