Comparative accuracy of mid-thigh soft tissue thickness and the hadlock formula in fetal weight estimation during the...

Accurate fetal weight estimation is crucial in prenatal care to prevent complications related to low birth weight or macrosomia. Conventional methods such as the Hadlock formula, based on biometric parameters, may lack accuracy, especially at weight extremes. Mid-thigh soft tissue thickness (MTSTT) has emerged as a promising, reproducible parameter for improved fetal weight estimation. This study aimed to compare the accuracy of mid-thigh soft tissue thickness (MTSTT) and the Hadlock formula in fetal weight estimation during the third trimester of pregnancy.

A prospective cross-sectional study was conducted on 300 term singleton pregnancies at Hospital (2023-2025). Standard fetal biometric parameters were measured using ultrasound, and estimated fetal weight (EFW) was calculated via both Hadlock and MTSTT-based formulas. Actual birth weight was recorded post-delivery. Correlations, error analysis, and ROC curves were used to compare predictive accuracy.

EFW using the MTSTT model showed a stronger correlation with Actual birth weight (r = 0.956, r² = 0.914) compared to the Hadlock method (r = 0.778, r² = 0.610). MTSTT-based estimation demonstrated higher accuracy, with 74 % of values within 5 % of Actual birth weight and an AUC of 0.992 for predicting macrosomia. Superior diagnostic performance was consistent across all birth weight categories.

MTSTT is a highly accurate and clinically feasible tool for fetal weight estimation. It outperforms the Hadlock formula, especially in extreme weight categories, and offers a reproducible alternative for routine obstetric practice.