Prenatal prediction of postnatal large‐for‐dates neonates using a simplified MRI method: comparison with conventional 2D ultrasound estimates

ABSTRACT Objective To evaluate the performance of a simple semi‐automated method for estimation of fetal weight (EFW) using magnetic resonance imaging (MRI) as compared with two‐dimensional (2D) ultrasound (US) for the prediction of large‐for‐dates neonates. Methods Data of two groups of women with singleton pregnancy between March 2011 and May 2016 were retrieved from our database and evaluated retrospectively: the first group included women who underwent US‐EFW and MRI‐EFW within 48 h before delivery and the second group included women who had these evaluations between 35 + 0 weeks and 37 + 6 weeks of gestation, more than 48 h before delivery. US‐EFW was based on Hadlock et al . and MRI‐EFW on the formula described by Baker et al . For MRI‐EFW, planimetric measurement of the fetal body volume (FBV) was performed using a semi‐automated method and the time required for measurement was noted. Outcome measure was the performance of MRI‐EFW vs US‐EFW in the prediction of large‐for‐dates neonates, both ≤ 48 h and > 48 h before delivery. Receiver–operating characteristics (ROC) curves for each method were compared using the DeLong method. Results Of the 270 women included in the first group, 48 (17.8%) newborns had birth weight ≥ 90 th centile and 30 (11.1%) ≥ 95 th centile. The second group included 83 women, and nine (10.8%) newborns had birth weight ≥ 95 th centile. Median time needed for FBV planimetric measurements in all 353 fetuses was 3.5 (range, 1.5–5.5) min. The area under the ROC curve (AUC) for prediction of large‐for‐dates neonates by prenatal MRI performed within 48 h before delivery was significantly higher than that by US (for birth weight ≥ 90 th centile, difference between AUCs = 0.085, standard error (SE) = 0.020, P < 0.001; for birth weight ≥ 95 th centile, difference between AUCs = 0.036, SE = 0.014, P = 0.01). Similarly, MRI‐EFW was better than US‐EFW in predicting birth weight ≥ 95 th centile when both examinations were performed > 48 h prior to delivery (difference between AUCs = 0.077, SE = 0.039, P = 0.045). Conclusion MRI planimetry using our purpose‐designed semi‐automated method is not time‐consuming. The predictive performance of MRI‐EFW performed immediately prior to or remote from delivery is significantly better than that of US‐EFW for the prediction of large‐for‐dates neonates. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.