Accuracy of Estimated Fetal Weight by Ultrasound Versus Leopold Maneuver

Estimated fetal weight (EFW) is frequently used for clinical decision-making in obstetrics. The goals of this study were to determine the accuracy of EFW assessments by Leopold and ultrasound and to investigate any associations with maternal characteristics. Postgraduate years 1 and 2 obstetrics and gynecology resident physicians from Harbor-UCLA Medical Center from 2014 to 2020 performed EFW assessments on 10 preterm (<37 weeks' gestational age) fetuses by ultrasound biometry and 10 full-term (≥37 weeks' gestational age) fetuses by ultrasound biometry and Leopold maneuver. Assessments were included if the patients delivered within 2 weeks of the assessments. One thousand six hundred ninety-seven EFW assessments on 1183 patients performed by 33 residents were analyzed; 72.6% of sonographic full-term EFWs, 69% of Leopold full-term EFWs, and 61.5% of sonographic preterm EFWs were within 10% of the neonatal birth weight (BW). The lowest estimation error in our study occurred when actual BW was 3600 to 3700 g. After adjusting for BW, residents were found to have lower accuracy when the mother had a higher body mass index (BMI) for full-term estimation methods (Leopold and ultrasound, β = 0.13 and 0.12, P = 0.001 and 0.002, respectively). Maternal BMI was not related to estimation error for preterm fetuses ( β = 0.01, P = 0.75). Clinical and sonographic EFW assessments performed by obstetrics and gynecology junior residents are within 10% of neonatal BW much of the time. In our cohort, they tended to overestimate EFWs of lower-BW infants and underestimate EFWs of higher-BW infants. Accuracy of full-term EFW assessments seems to decrease with increasing maternal BMI.