Abstract / Summary
Abstract Background Accurate estimation of fetal weight is important for obstetric decision-making and identification of fetuses at risk of adverse perinatal outcomes. Although ultrasound-based estimation is widely used, clinical methods remain important in settings where access to ultrasound is limited. This study compared the accuracy of clinical and ultrasound-based fetal weight estimation with actual birth weight in term pregnancies and assessed the influence of maternal body mass index (BMI) on clinical estimation. Methods This prospective cohort study included 200 women with singleton term pregnancies between 37 and 41 + 6 weeks of gestation who were expected to deliver within 72 hours at Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi. Clinical estimated fetal weight (EFW) was calculated using Johnson’s formula based on symphysis-fundal height and fetal head station. Ultrasound EFW was calculated using Hadlock’s formula based on fetal biometric measurements. Both estimates were compared with actual birth weight (ABW). Correlation, mean differences, estimation accuracy within 10% of ABW, and agreement were assessed. The influence of maternal BMI on clinical estimation accuracy was also evaluated. Results The mean clinical EFW was 3060 ± 320 g, compared with 3180 ± 330 g by ultrasound and 3110 ± 350 g for ABW. Both clinical and ultrasound estimates were significantly correlated with ABW, with stronger correlation for ultrasound (r = 0.89, p < 0.001) than for clinical estimation (r = 0.76, p < 0.001). The proportion of estimates within 10% of ABW was higher with ultrasound than with clinical estimation (78.5% vs. 62.0%). Clinical estimation showed increasing underestimation with higher maternal BMI, with a mean difference from ABW of 30 ± 170 g in women with BMI < 25 kg/m², − 60 ± 180 g in those with BMI 25–29.9 kg/m², and − 130 ± 200 g in those with BMI ≥ 30 kg/m². Conclusion Ultrasound-based fetal weight estimation demonstrated greater correlation and accuracy with actual birth weight than clinical estimation in term pregnancies. Clinical estimation using Johnson’s formula nevertheless provides a practical and accessible alternative where ultrasound is unavailable, particularly in resource-limited settings. Maternal BMI should be considered when interpreting clinically estimated fetal weight, as accuracy may decrease with increasing BMI.