Background: Estimation of fetal weight is important for antenatal and intrapartum management of pregnant women. Sonographic methods are not readily accessible in under-resourced settings, it is therefore necessary to study the accuracy of a clinical method of estimating fetal weight where this limitation (unavailability of ultrasound) exists.
Objective: To compare the accuracy of clinical and ultrasound methods of fetal weight estimation at term.
Materials and methods: Clinical and ultrasound fetal weights were estimated on 200 consecutive term pregnancies (37 completed weeks of gestation - 41 weeks and 6 days) at the University of Nigeria Teaching Hospital, Enugu, Nigeria from 1 st April to 30 th November 2012. Accuracy was determined using percentage error, absolute percentage error, and proportion of estimates within 10% of actual birth weight.
Results: Actual birth weight had strong positive correlation with both clinical and ultrasound estimated fetal weights (r = 0.71, P < 0.001 and r = 0.69, P < 0.001, respectively). Overall, both the clinical and ultrasound methods systematically overestimated the actual birth weight. The proportion of the clinical estimated weights that were within 10% of the actual birth weight was significantly lower than that of ultrasound method for babies of all birth weights (35.0 vs. 67.5%; P < 0.001) and for macrosomic babies (76 vs 100%, P = 0.009). For babies with normal birth weights (2.5-3.9 kg), ultrasound method error values were significantly lower than those of clinical method for both the mean % error (5.4 vs 19.6%; P < 0.001) and the mean absolute % error (9.97 vs 20.6%; P < 0.001).
Conclusion: The ultrasound method is generally a better predictor of the actual birth weight than the clinical method, and thus should be used in estimating the actual birth weight when accessible.