Magnetic resonance imaging compared to ultrasonography in fetal weight and volume estimation in diabetic and normal pregnancy.

OBJECTIVE: To estimate fetal volume and weight in diabetic and normal pregnancy using high-resolution magnetic resonance imaging.
METHODS: T1-weighted magnetic resonance imaging was combined with semiautomatic segmentation technique. The accuracy of fetal volume estimations thus obtained was compared with conventional ultrasound-based weight estimations in ten pregnant women with insulin-dependent diabetes mellitus and ten women with normal pregnancy. Examinations were made within 48 hours before delivery.
RESULTS: Ultrasound-based estimations of fetal weight showed a correlation rate of r=0.77 with the actual birth weights in the whole material, while volume determinations based on magnetic resonance imaging showed a significantly better correlation rate of r=0.95. Diabetic women did not differ from the normal pregnancy group with regard to birth weight or the accuracy of weight estimations.
CONCLUSIONS: High-resolution magnetic resonance imaging combined with semiautomatic segmentation software was found to be accurate in determining fetal volume and, consequently, better than conventional ultrasound-based techniques in estimating fetal weight. The use of magnetic resonance imaging in fetal weight estimation may be recommended for clinical situations where an accurate weight estimate is considered essential.