Accuracy of Clinical and Sonographic Estimations of Fetal Weight at Term at the Federal Teaching Hospital, Gombe Nigeria

Abstract

Background: Accurate estimation of fetal weight is important in making appropriate management decision. For example, the decision on the mode of delivery of suspected cases of fetal macrosomia, maternal diabetes, vaginal birth after caesarean section and breech deliveries, is largely dependent on estimation of fetal weight. It is also used by the obstetricians in counselling pregnant women on the timing of delivery of intrauterine growth restricted fetuses. There are inconsistent reports from the clinical and ultrasonographic fetal weight estimation methods. Aim: The aim of the study was to estimate the fetal weight using both clinical and sonographic methods and to determine their accuracy by comparing them with actual birth weight. Methods and Materials: This was a prospective cross-sectional comparative study. One hundred and twenty-two pregnant women who were admitted for delivery within 36 hours were consecutively recruited. The birth weights of the fetuses were estimated using Dare’s clinical formula and Hadlock’s ultrasound formula. The women were followed up till delivery and the birth weight of the neonates were taken within 20 minutes of delivery. Results: In the entire study group, the clinical method overestimated the birth weight by an average of 241 g while sonographic method underestimated the birth weight by an average of 50 g. The mean of the absolute percentage error was higher in the clinical method compared with the sonographic method (11.06% vs. 8.85%; P value = 0.008). The proportions of the estimates within 10% of the actual birth weight were higher with sonographic estimation compared with the clinical estimation (64.8% vs. 46.7%; p-value = 0.240). Conclusion: Ultrasound is a better predictor of the actual birth weight and should be used where fetal weight is critical in decision making.