Factors Influencing the Accuracy of Sonographyestimated Fetal Weight:A Retrospective Cohort Study in the Chinese Population

Objective:To evaluate the accuracy of sonography-estimated fetal weight(EFW)and to determine the potential factors influencing EFW accuracy in the Chinese population.Methods:Eleven widely used formulae were chosen to evaluate the accuracy of EFW in 7016 cases in a retrospective cohort study.Nine potential factors(prenatal body mass index[BMI],gestational age[GA],birth weight[BW],fetal sex,fetal presentation,amniotic fluid volume[AFV],seniority of sonographers,the time interval between ultrasonic measurement and delivery,and diabetes mellitus)were analyzed by binary logistic regression to determine whether they influenced sonography-EFW.Results:All 11 models had high correlation coefficients between EFW and BW(r=0.819–0.843).Model 3 was the most accurate formula for the Chinese population.Compared to fetuses with EFW of 2500–3999g,the accuracy of EFW decreased by 69.10%(P<0.001)for fetuses less than 2500g,and decreased by 54.10%(P<0.001)for fetuses larger than 4000g.The accuracy of EFW in female fetuses decreased by 12.70%compared with male fetuses(P=0.021).Compared to the EFW calculated 1-3 days before delivery,the accuracy of the EFW performed 4–7 days before delivery showed a significant decrease(P=0.014).The accuracy of EFW was influenced by the individual measurement accuracy of the sonographers.Maternal BMI,DM,GA,fetal presentation,and AFV did not influence the accuracy of EFW after adjustment.Conclusion:Model 3 was the most accurate model for the Chinese population.The BW,fetal sex,time interval,and technique of the sonographers had different influences on the accuracy of EFW.