Comparison of Clinical Methods for Estimating Fetal Weight During Labor with Actual Birth Weight

Abstract

This comparative descriptive study aimed to assess the accuracy of four clinical methods for estimating fetal weight Dare’s formula, Johnson’s formula, Khajornsiri Phongsawasdikul’s equation, and Nusara Puarrattanarunkorn’s equation against actual birth weight. The sample comprised 115 women who delivered at the labor room of Sing Buri Hospital between October 1, 2023, and September 30, 2024, and met the eligibility criteria. Fundal height, abdominal circumference, fetal station, and actual birth weight were recorded. Estimated fetal weight was calculated using each method. Data were analyzed using descriptive statistics, repeated-measures analysis of variance, and Bonferroni-adjusted pairwise comparisons.

The mean actual birth weight was 3,224.84± 363.87 g. Estimates from all four methods differed significantly from actual birth weight (p < .001). Based on the reported error measures, Khajornsiri Phongsawasdikul’s equation yielded the smallest estimation error, followed by Johnson’s formula, Nusara Puarrattanarunkorn’s equation, and Dare’s formula, respectively.

Khajornsiri Phongsawasdikul’s equation produced the closest estimate of actual birth weight in this sample. It may be used as an initial screening tool to support risk assessment and care planning during labor; however, it should be interpreted together with other clinical findings and obstetric assessment, particularly when fetal growth restriction or macrosomia is suspected.