Clinical assessment of Fetal weight estimation using Johnson's formula & Ultrasonographic assessment using Hadlock's formula at or near term: A comparative observational study

Abstract—Fetal weight in conjuction with gestational age is an important indicator of pregnancy outcome. So this study was conducted to find out the better method among using Johnson's formula or using Hadlock's formula to estimate fetal weight antenatally at or near term. This prospective study conducted on 100 pregnant women selected by simple random sampling with single term pregnancy with no fetal anomalies, delivered within one week of ultrasonography as well as measuring the symphysiofundal height and accuracy of Johnson's and Hadlock's formula compared. Fetal Weight is overestimated in all groups by Johnson's formula whereas in Hadlock’s formula there is underestimation of birth weight <2500 gms and >3500 gms babies and overestimation between 2500-3500 gms babies. The correct weight was estimated with an error of 100gms in 30% of cases by Johnson’s formula and in 68% of cases by ultrasound Hadlock's method. Although Hadlock's formula was found relatively more accurate than Johnson's formula in predicting birth weight but Johnson's formula is a quick, easy, accurate, reliable and cost effective method for estimating the fetal weight in remote areas where ultrasound is not available if assessed by experienced obstetricians. Despite the superiority of ultrasonography the simple clinical method of predicting fetal weight is of great value especially in developing countries.