ORIGINAL RESEARCH article
Front. Med.
Sec. Obstetrics and Gynecology
Influencing factors on accuracy of third-trimester ultrasound detection of fetal weight
Shihua Deng
Huixian Pang
Ningzhu Jiang
Wei Jiang
Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, China
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Abstract
Background: Accurate estimation of fetal weight (EFW) in the third trimester is critical for managing deliveries and reducing perinatal complications. This study aimed to investigate factors influencing the accuracy of third-trimester ultrasound fetal weight estimation in pregnant women with full-term, single pregnancies. Methods: This retrospective cohort study included 284 pregnant women who delivered either vaginally or via elective cesarean section between January 2022 and December 2023. Exclusion criteria were preterm labor, abnormal fetal positioning, multiple pregnancies, maternal obesity (BMI ≥30 kg/m²), and other complications. Ultrasound fetal weight measurements were conducted using a digital ultrasonic diagnostic system (Dp3300), and accuracy was assessed by comparing estimated fetal weight (EFW) to actual birth weight (ABW) within 30 minutes of birth. The mean absolute percentage error (MAPE) was calculated, and cases were categorized into low error (≤ 10%) and high error (> 10%) groups. Results: Significant differences were observed between accurate and inaccurate groups in maternal age (31.1 ± 5.21 years vs. 33.51 ± 5.31 years, P = 0.002), BMI at delivery (29.84 ± 4.52 kg/m² vs. 28.02 ± 4.85 kg/m², P = 0.008), and interval between ultrasound and delivery. Higher EFW errors were associated with greater fetal weight (3588.57 ± 508.44 g vs. 3409.21 ± 435.07 g, P = 0.014) and length (51.24 ± 5.08 cm vs. 47.65 ± 4.35 cm, P < 0.001). Logistic regression identified significant associations with maternal age (OR, 1.101; P = 0.004), BMI at delivery (OR, 1.097; P = 0.019), fetal weight (OR, 1.001; P = 0.014), fetal length (OR, 1.167; P < 0.001), and interval between ultrasound and delivery (OR, 7.523; P < 0.001). ROC analysis showed the strongest predictor of error was the interval between ultrasound and delivery (AUC = 0.718). Conclusion: Advanced maternal age, higher BMI at delivery, greater fetal weight and length, and a longer interval between ultrasound and delivery are associated with less accurate third-trimester ultrasound fetal weight estimations. The interval between ultrasound and delivery emerged as the most significant predictor, highlighting the need for close monitoring and time-sensitive ultrasound evaluations to improve accuracy.
Summary
Keywords
Fetal Weight, Influence factor, pregnant, Third Trimester, Ultrasound estimation
Received
25 July 2025
Accepted
27 January 2026
Copyright
© 2026 Deng, Pang, Jiang and Jiang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Wei Jiang
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