Comparative Study on Johnson’s Formula, Insler’s Formula and Hadlock’s Formula for Estimating Foetal Weight at Term

Abstract

BACKGROUND Foetal weight is one of the greatest factor determining the survival of the foetus. Estimation of foetal weight predelivery helps to decide the mode of delivery and anticipate problems during labour. Aim of the study is to assess the foetal weight in term pregnancies by various methods, i.e. abdominal girth x symphysiofundal height (Insler's Formula), Johnson's formula and Hadlock's formula using USG to study the accuracy of these methods and to correlate these methods of estimation of foetal weight with actual birth weight of the baby after delivery. MATERIALS AND METHODS 200 cases having term pregnancies were selected from antenatal clinics and maternity wards in whom delivery was anticipated within one week of foetal weight estimation. Foetal weight estimation was done clinically by two methods, i.e. AG x SFH, Johnson's formula and by ultrasound using Hadlock's formula. Results were compared to the actual weight of the babies after delivery with respect to mean birth weight±SD and average error in estimating foetal weight and prediction of birth weight within 10% of actual birth weight. Statistical analysis was done using Student's t-test, Pearson's correlation. RESULTS The mean birth weight by symphysiofundal height * abdominal girth±SD was 2967.79±348.52 whereas mean of actual birth weight±SD was 2903±460.02. The p value calculated to be 0.118, which is statistically not significant. Average error in estimating foetal weight was 189.2 g by Hadlock's formula and 304.2 g by AG x SFH method. The difference is not statistically significant. Prediction of birth weight within 10% of actual birth weight was in 63.5% of cases by AG x SFH formula, 81% by Hadlock's formula and 49% by Johnson's formula. CONCLUSION AG x SFH (Insler's formula) has better predictable results is foetal weight estimation as difference between it and actual birth weight is not statistically significant making SFH * AG method more accurate for estimation of foetal weight if compared to actual birth weight. So, it can be of great value in a developing country like ours where ultrasound is not available at many healthcare delivery systems.

Comparative study of various methods of fetal weight estimation at term pregnancy in a tertiary hospital in Kanchipuram, Tamil Nadu, India

“…The results corroborate with that the study of Nayak and others which reported that prediction of fetal weight by clinical method was as accurate as the ultrasonographic method. 16 Majority of the studies including the present study reported USG was superior to clinical method in estimating fetal weight in terms of percentage error. 1,17 On the other hand, a few studies showed that clinical method has the same accuracy or even better than USG.…”

“…15 As reported by Nayak and others the results of the study also showed that least average error was observed with USG while least standard error was observed with Dare's formula and the values were closer between USG and Dare's method. 16 Comparison results showed that both USG and Dare's predictions are closer to the actual baby weight and hence Dare's method can be considered an alternative method in the absence of USG. The results corroborate with that the study of Nayak and others which reported that prediction of fetal weight by clinical method was as accurate as the ultrasonographic method.…”

Comparison of Actual Birth Weight with the Ultrasonographic and Clinical Estimation of Fetal Birth Weight: A Prospective Study

“…8 However, Nayak et al conducted a study which showed that the fetal weight estimation the clinical method was as accurate as of the ultrasound method. 18 Some studies have shown that the clinical method has the same accuracy or even better than USG. 19,20 This study has shown that the ultrasound method of fetal weight estimation was more accurate than the clinical estimation of fetal weight estimation which is similar to the studies done by Ugwa et al and Chauhan and coworkers.…”

Comparative study of clinical assessment of fetal weight estimation using Johnson’s formula and ultrasonographic assessment using Handlock’s formula at or near term and its correlation with its actual birth weight

“…Fetal weight in conjuction with gestational age is an important indicator of pregnancy outcome. 2 Two main methods for predicting birth-weight in current obstetrics were used: (a) Clinical techniques based on abdominal palpation fetal parts and calculations based on fundal height and (b) Sonographic measures of skeletal fetal parts, which are then inserted into regression equations to derive estimated fetal weight. 3 Evaluation of uterine size externally with use of a physician's hand is characterized by being simple, easy and cheap.…”