# Comparison of Hadlock and INTERGROWTH-21st Growth Charts for Estimating Fetal Weight in the Third Trimester via Ultrasound

## TL;DR

This study compares two fetal weight estimation charts, Hadlock and INTERGROWTH-21st, to determine their accuracy in predicting fetal weight during the third trimester using ultrasound.

## Contribution

The study provides empirical evidence comparing the diagnostic accuracy of Hadlock and INTERGROWTH-21st growth charts in estimating fetal weight in the third trimester.

## Key findings

- Both Hadlock and IG 21 charts showed strong positive correlations in estimating fetal weight at both 32-34 weeks and 38-40 weeks gestation.
- For every 1 g increase in estimated fetal weight by Hadlock, birth weight increased by 0.86 g, and by 0.82 g for IG 21.
- Both charts demonstrated fair agreement with estimated fetal weight in early and late third trimester scans.

## Abstract

Introduction

Early identification of growth abnormalities is crucial in preventing fetal death and ensuring optimal care for fetuses requiring close monitoring and timely delivery. Sonographic estimation of fetal weight must be quantified in centiles according to gestational age reference charts to assess fetal growth velocity and size. These measurements can categorize the fetus as small, appropriate, or large for gestational age. Recent discussions have highlighted the increasing need for evidence-based guidelines for selecting the most suitable growth charts.

Objectives

The objective of this study is to compare the diagnostic accuracy of Hadlock versus INTERGROWTH 21st (IG 21) growth charts for estimating fetal weight.

Methods

This is a prospective cohort study conducted on 277 pregnant women with singleton fetuses at 32-34 weeks of gestation in the Department of Obstetrics and Gynecology at a tertiary care referral center in North India. The participants underwent two ultrasound scans, first at the 32- to 34-week period of gestation (POG) and then a second ultrasound scan at the 38- to 40-week POG or one week before delivery. Labor and delivery outcomes were noted, and neonatal weight was recorded. The mother and neonate were observed for any perinatal complications till discharge from the hospital.

Results

The mean POG at the first scan was 33.00 weeks. At the first scan, the mean of estimated fetal weight (EFW) by Hadlock was 1966.96 g. The mean of EFW by IG 21 was 1861.50 g. There was a strong positive correlation between EFW by IG 21 and EFW by Hadlock in the first scan, and this correlation was statistically significant (r = 0.78, p ≤ 0.001). The mean POG at the second scan was 38.63 weeks. The mean of EFW in the second scan by Hadlock was 2905.24 g. The mean of EFW in the second scan by IG 21 was 2829.32 g. There was a strong positive correlation between EFW by IG 21 and EFW by Hadlock in the second scan, and it was statistically significant (r = 0.71, p ≤ 0.001). For every 1 g increment in EFW on the second scan by Hadlock, the birth weight (g) increases by 0.86 g. For every 1 g increment in EFW on the second scan by IG 21, the birth weight increases by 0.82 g.

Conclusion

Both Hadlock and IG 21 charts have a fair agreement with EFW in early and late trimester scans. Hence, either one of the two can be used for fetal biometry.