A comparative study of fetal weight estimation using Johnson’s formula and ultrasound and their correlation with actual birth weight

Abstract

Objectives: This study was aimed to compare and correlate the accurate estimation of foetal weight (EFW) obtained by clinical method (cEFW) and ultrasonographically (uEFW) with actual birth weight (ABW). Methods: This hospital based prospective comparative study was done in a tertiary care teaching hospital situated in South India, from January 2017 to December 2019 on 200 antenatal pregnant women with singleton pregnancy. Results: The mean maternal age was 23.74±3.60 years. Most of the women (43%) belonged class 3 socio economic strata. The mean BMI was 23.34±3.29 Kg/m2. LSCS was more common than (60.50%) vaginal delivery (37.50%). The mean cEFW was 2997.30±420.06 gm, uEFW was 2768.91±412.01 gm and ABW was 2765.05±412.89 gm (p<0.001). The kappa agreement between ABW and uEFW was 0.532 with SE of 0.048 and it was 0.022 with 5.688 for cEFW respectively. The mean percentage difference between cEFW and uEFW with ABW (9.43±14.26 and 0.45± 8.15; p<0.001) was statistically significant. There was significant strong positive correlation between ABW and uEFW (ρ=0.836; R2=0.728; p<0.001) as well as cEFW (ρ=0.641; R2=0.4082; p<0.001). Conclusion: Clinical estimation of birth weight being simple and cost effective definitely has a role in the management of labour and delivery but the ultrasound derived EFW seems to be more valid and accurate than clinical method as it is highly reproducible.

Keywords

• estimated fetal weight
• hadlock’s formula
• johnson’s formula
• symphysio-fundal height