Estimated fetal weight accuracy in pregnancies with preterm prelabor rupture of membranes by the Hadlock method

Abstract

Objective We aimed to assess the accuracy of the estimated fetal weight (EFW) to predict the birthweigth (BW) in pregnancies complicated by PPROM. Study design This study was a secondary analysis of a prospective cohort of pregnancies with PPROM. We included singleton pregnancies from 23 to 36 + 6 weeks, mothers from 13 to 46 years of age, and those with an EFW within two weeks of delivery. We excluded pregnancies with complex fetal anomalies and fetal demise. The accuracy of the EFW was determined by the absolute percent difference between BW and EFW ([BW-EFW]/BW*100%). T tests and linear regression were performed for statistical analysis. Results The mean percent difference of BW vs. EFW was 8.72 ± 6.94%. The EFW was more accurate (8.24 ± 6.81 vs. 13.31 ± 6.88%, p = .027) and had more measurements with a absolute difference < 10% (70% vs. 30%; p = .034) when performed within seven days of delivery. The EFW accuracy decreased with anhydramnios (11.37 ± 7.06 vs. 7.69 ± 6.77%, p = .020), but the measurements with an absolute difference <10% was not significantly different (p = .27) with anhydramnios. Conclusion In PPROM, the EFW within seven days to delivery by Hadlock accurately predicts the birthweight with a mean absolute difference of 8.2%. Brief rationale There are a limited number of studies evaluating the accuracy of the EFW in pregnancies with PPROM in the last four decades.