Analysis of the accuracy of ultrasound formula in estimating fetal weight in low-risk full-term pregnant women

Background The use of ultrasound formulas to estimate fetal weight has become an important clinical tool. Many hospitals in China choose Hadlock formula 1 as the preferred formula. But many scholars and clinicians still have doubts about whether Hadlock Formula 1 is applicable to Chinese pregnant women. Methods This retrospective study analyzed the clinical and ultrasound data of 390 low-risk, term, singleton live-born pregnant women who delivered between December 1, 2023, and February 28, 2025. And we analyzed the difference between the actual newborn weight of low-risk pregnant women and the EFW of four formulas (Hadlock formula 1/2/3, Ott formula) to verify the accuracy of Hadlock formula 1 in low-risk, full-term, singleton pregnant women and explore the potential factors that affect its accuracy. Results The Mean Percentage Error (MPE), Mean Absolute Percentage Error (MAPE), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE) values of Hadlock formula 1 and Ott formula were significantly lower than those of other formulas. According to the accuracy ranking based on Euclidean distance, Hadlock formula 1 ranked first. Compared with ultrasound physicians with less than 5 years of experience, those with more than 5 years of experience had a significantly lower risk of overestimating fetal weight when using Hadlock formula 1. Neonatal female sex was associated with a significantly increased risk of overestimation using Hadlock formula 1 compared with male sex. Conclusions The use of Hadlock formula 1 for fetal weight estimation in low-risk, full-term, singleton Chinese pregnant women is more accurate than the other three Hadlock formulas or the Ott formula.