Body weight lower limits of fetal postmortem MRI at 1.5 T

Objective To evaluate the diagnostic yield of postmortem magnetic resonance imaging (PM-MRI) compared with conventional autopsy in fetuses of early gestational age and low body weight. Methods Fetuses of < 31 weeks' gestation that underwent 1.5-T PM-MRI and conventional autopsy were included. The findings of PM-MRI and conventional autopsy were reported blinded to each other. The reports of conventional autopsy and PM-MRI for each organ system (cardiovascular, neurological, abdominal, non-cardiac thoracic and musculoskeletal) were classified as either diagnostic or non-diagnostic. The likelihood of a non-diagnostic examination by PM-MRI was calculated according to fetal gestational age and body weight. Results Full datasets were examined of 204 fetuses, with mean gestational age of 20.95 +/- 3.82 weeks (range, 12.0-30.7 weeks) and body-weight range of 15.9-1872 g. Body weight was the most significant predictor of diagnostic yield of PM-MRI. There was 95% confidence that 90% of fetuses will show diagnostic images by PM-MRI for all five organ systems when fetal body weight is >= 535 g, but < 50% of fetuses will have all five systems diagnostic on PM-MRI when body weight is < 122 g. Conclusion PM-MRI is highly likely to provide adequate diagnostic images for fetuses with a body weight > 500 g. Below this weight, the diagnostic yield of standard 1.5-T PM-MRI decreases significantly. These data should help inform parents and clinicians on the suitability of performing PM-MRI in fetuses with low body weight. Copyright (C) 2015 ISUOG. Published by John Wiley & Sons Ltd.