Fetal weight estimation in tall women: is ultrasound more accurate than clinical assessment? A prospective trial.

ABSTRACT

PURPOSE: Estimated fetal weight (EFW) is crucial for clinical decision-making during pregnancy and labor. Maternal habitus impacts its accuracy. This study compared the accuracy of clinical versus ultrasound EFW in tall pregnant women (height ≥ 172 cm, 90th percentile). METHODS: In this prospective study, tall pregnant women at term, who arrived for a prenatal visit and delivered within a week, underwent clinical and ultrasound assessments of estimated fetal weight. Each woman served as her own control. After delivery, birth weight was compared to the clinical and ultrasound EFW. The primary outcome was the accuracy of each method in predicting the actual birth weight. RESULTS: All 100 women included in this trial underwent clinical and ultrasound estimations of fetal weight. Mean maternal height was 175.7 ± 3.3 (172-185) cm. More clinical EFW swere inaccurate compared to ultrasound (25 (25%) vs. 6 (6%), respectively, p < 0.001). Both clinical (3583 g) and ultrasound (3490 g) evaluations underestimated the fetal weights compared to the birth weights (3664 g, p < 0.001). In the macrosomic fetal group, both the clinical (3983 g) and ultrasound (3767 g) estimates were significantly inaccurate compared to the birth weights (4237 g, p < 0.001). CONCLUSION: Among tall women, ultrasound EFW is more accurate than clinical EFW. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION IRB-0016-17-MMC, Clinical-Trials.gov identifier NCT03206281.