Ultrasound prediction of birthweight and growth restriction in fetal gastroschisis

Objective: Most ultrasound estimated fetal weight (EFW) formulas incorporate abdominal circumference, which may overstimate growth restriction in fetal gastroschisis. The aim of this study was to determine the optimal ultrasound formula for prediction of birthweight and fetal growth restriction (FGR) in gastroschisis. Study Design: We conducted a retrospective cohort analysis of singleton fetuses with gastroschisis. Percentage of error between ultrasound EFW (performed within 2 weeks of delivery) and birthweight was calculated. Agreement between EFW by ultrasound formulas and birthweight was determined by Bland-Altman limits of agreement; concordance between ultrasound and birthweight diagnosis of FGR was evaluated with McNemar's test. Results: Birthweight was best predicted by the formulas of Shepard et al and Siemer et al. Only these formulas demonstrated significant agreement with birthweight for prediction of FGR at the 5th and 10th percentiles. Conclusion: The formulas of Shepard et al and Siemer et al best estimate birthweight, and their use has the potential to reduce rates of overdiagnosis of FGR.