Estimation of fetal weight: a comparison of clinical and sonographic methods

Fetal weight estimation is important in the management of labour and delivery. This study aimed to compare the accuracy of the clinical and ultrasound methods of fetal weight estimation. This was a prospective study involving 110 term cephalic singleton pregnancies delivered within 24 hours of clinical fetal weight estimation using Johnson's and Dare's formulae and ultrasound estimation at a Tertiary hospital in Abakaliki, Nigeria. The data were analysed with Stata 11 software. The sonographic estimation within 10% of the actual birth weight (ABW) of 68.2% was significantly greater than the accuracy of Johnson's (23.6%), Dare's (26.4%), and the combined clinical formulae (27.1%). The clinical methods overestimated the fetal weight. Both methods showed a positive correlation with the ABW. In conclusion, the sonographic method had a better accuracy than the clinical methods. However, fetal weight overestimation by clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude fear of complications from macrosomia. Impact statement What is already known on this subject? An accurate estimation of fetal weight is important in the management of labour and delivery. However, there is limited evidence that any of the available methods of fetal weight estimation is more accurate than the others. What do the results of this study add? This study showed that the clinical methods using Johnson's and Dare's formulae had a significantly higher mean percentage and absolute mean percentage error compared to the sonographic estimation of fetal weight. The sonographic estimation within 10% of actual birth weight (ABW) of 68.2% was significantly greater than that of Johnson's and Dare's formulae with 23.6% and 26.4%, respectively. All of the methods showed a positive correlation with the ABW. What are the implications of these findings for clinical practice and/or further research? This implies that the sonographic method has a better accuracy than the clinical methods in estimating the fetal weight. However, the overestimation of fetal weight by the clinical methods warrants their usefulness in resource-poor settings such that the clinical determination of a normal weight foetus will exclude the fear of complications from macrosomia.