Detection of Adverse Perinatal Outcomes at Term Delivery Using Ultrasound Estimated Percentile Weight at 35 Weeks of Gestation: Comparison of Five Fetal Growth Standards

Abstract

Objective: To assess the predictive ability of the ultrasound estimated percentile weight (EPW) at 35 weeks of pregnancy to predict adverse perinatal outcomes (APOs) at term delivery according to 5 fetal growth standards, including population, population-customized, and international references. Methods: This was a retrospective cohort study of 9,585 singleton pregnancies. Maternal clinical characteristics, fetal ultrasound data obtained at 35 weeks and pregnancy and perinatal outcomes were used to calculate EPWs to predict APOs according to: the customized and noncustomized (NC) Miguel Servet University Hospital (MSUH), the customized Figueras, the NC INTERGROWTH-21st, and the NC World Health Organization (WHO) international standards. APOs were defined as the occurrence of cesarean or instrumental delivery for nonreassuring fetal status, 5-min Apgar score < 7, arterial cord blood pH <7.10, or stillbirth. The predictive ability of EPW for APOs was analyzed using the area under the curve (AUC), and sensitivities were calculated for different false-positive rates (FPRs). Results: For a 10% FPR, detection rates for total APOs ranged between 12.7% with the customized MSUH (AUC 0.52; 95% CI 0.50–0.55) and 14.4% with the NC MSUH standard (AUC 0.55; 95% CI 0.53–0.57) for EPW by ultrasound; and from 22.0% with the customized MSUH standard (AUC 0.60; 95% CI 0.58–0.63) to 27.8% with the NC WHO (AUC 0.65; 95% CI 0.63–0.68) for EPW at delivery. Conclusions: The predictive capacity of the EPW for APOS is limited and similar, by both ultrasound and at delivery, for the 5 growth standards, without significant differences between customized and NC standards.