Standards for Fetal Abdominal Circumference and Estimated Fetal Weight in Shanghai, China

Introduction: While current evidence suggests that fetal skeletal parameters do not vary considerably across populations, there is uncertainty about the standards of abdominal circumference (AC) and estimated fetal weight (EFW), which are the basis of clinical guidelines for the management of fetal growth restriction. The use of different algorithms for mapping ultrasound parameters to fetal size parameters also make it difficult to make local applications of growth standards developed elsewhere. Therefore, we aimed to construct standards of AC and EFW for use in China.Methods: This is an analysis of pregnant women who received antenatal care from 2009 to 2013 in Shanghai, China. A healthy cohort of 2529 singleton pregnancies defined by maternal, pregnancy and fetal characteristics and birth outcomes were selected for analysis. Ultrasound measurement was used to estimate gestational age and the Hadlock algorithm was used to calculate EFW.Results: A linear increase of AC was observed from 16 to 35 weeks, after which the increase slightly flattened out. An accelerating increase of EFW was observed from 16 to 27 weeks, after which the increase became linear and then flattened out around 36 weeks. Model diagnostics showed sufficient goodness-of-fit of the standards.Conclusion: Standards of AC and EFW are available to monitor fetal growth for pregnancy in China. Comparability with other cohorts cannot be conclusive as different analysis methods were used across studies.