Accuracy of Estimated Fetal Weight in Third Trimester [33A

Abstract

INTRODUCTION: The aim of our study is to determine whether fetal growth scans that are performed after 37 weeks gestation can be relied upon to give an accurate estimation of fetal weight (EFW), and also help to guide antenatal management with delivery recommendations. Due to the inherent error associated with ultrasound measurements, the accepted overall margin of error between EFW and actual birth weight (ABW) is 15%. METHODS: A retrospective descriptive qualitative study with a total of 1785 cases, where the EFW was obtained within 3 weeks of delivery were compared with ABW. The significant difference between EFW and ABW was tested by paired t-test. Pearson's correlation was used to detect significant linear relationship. The difference in error rates among the weight and GA categories were assessed by chi-square test. RESULTS: The error rates of <15% <10% and <5% for GA of 37 to 40 weeks was seen as 86%, 68% and 38% respectively. The error rate of <15% for GA of <37 weeks was lower when compared to the GA in other categories (P=.0227). CONCLUSION: Our estimated fetal weight measurements at 37 weeks and beyond may be considered accurate as our error rate is below the acceptable rate of <15%. Despite the popular consensus of inaccurate late third trimester EFW, we found that with increasing gestational age and increased ABW, our EFW are within acceptable error rates. In order to utilize our EFW measurements for antenatal management and delivery recommendations, improvements in our biometric measurements should strive for improved error rates of <5–10%.