Two new models for the estimation of foetal weight more than a week before delivery: An MRI study

To develop and evaluate new formulas to determine the magnetic resonance imaging (MRI)-based estimated foetal weight (EFW) more than a week before delivery.

The study included 153 women with singleton pregnancies who gave birth to live, normal neonates within 15-21 days of the MRI examination for whom foetal body volume biometry data were available at term. All foetuses were randomly divided into a testing group (102) and a validation group (51). Regression analysis was used to determine the single volume or the combination of volume and MRI-to-delivery interval that determined the EFW. The accuracy of the two new models and the primary existing model developed by Baker et al. were evaluated in validation group.

The two new models had similar mean percentage errors (MPEs) (3.9% vs 3.9%) and proportions of pregnancies with an MPE < 10% (92.2% vs 90.2%); the model incorporating volume and MRI-to-delivery had relatively higher proportions of pregnancies with an MPE < 5% (72.5% vs 64.7%) and EFWs in agreement with the birth weights. The error in the Baker model was almost twice that in the new models.

The accuracy of foetal weight estimation more than one week before delivery using the model developed by Baker et al. was poor and was significantly improved by the new models. A combination of the foetal body volume and MRI-to-delivery interval will enable the more accurate determination of the EFWs.