Accuracy in Fetal Weight Estimation by Ultrasound: A Comparative Study of Hiwale and Hadlock Methods in a Tertiary Care Hospital.

Abstract

Background: Of all the methods available for fetal weight estimation, ultrasound-based estimation is the commonly used noninvasive and widely available technique. Different population-based models use a combination of fetal measurements for the estimation of fetal weight by ultrasound. Models developed for non-Indian populations give erroneous fetal weight estimates when used for Indian populations. Therefore, there is an immense need to develop an Indian-based model for sonographic fetal weight estimation. This study assesses the fetal weight from different available formulae and compares them with the actual birthweight.

Methodology: This was a prospective study of 154 women assessed by ultrasound within a week of delivery. Ultrasonogram was done and head circumference, biparietal diameter, abdominal circumference and femur length were measured and estimated fetal weight was calculated using Hadlock's formula and Hiwale formula. Actual birth weight of the baby was measured after the delivery. Estimated fetal weight predicted by each formula was compared with respective neonatal actual birth weight.

Results: Out of 154 pregnant women included in the study, 92.8% were of average reproductive age-group, i.e., 20-34 years with minimum age being 18 year and maximum age is 42 year. Birth weight ranged from 780 to 4200 gms, with a mean of 2619.6. Low birthweight babies constituted 34.3% (N = 53). In our study, when weight was calculated using Hiwale method nearly 25.3% of cases had overestimated and 74.7% had underestimated the fetal weight, out of it 45.5% of cases were within the range of ± 10% of the actual birthweight. The difference between mean estimated fetal weight and mean actual birth weight was 194.5 g.

Conclusion: Hadlock's method of fetal weight estimation was found to be more accurate.