Intrauterine versus post-mortem magnetic resonance in second trimester termination of pregnancy for central nervous system abnormalities

Objective: To evaluate if limiting factors of intrauterine magnetic resonance imaging (iuMRI) performed in the early second trimester of pregnancy (19–23 weeks) affect its accuracy in comparison to post-mortem MRI (pmMRI) in fetuses that underwent termination of pregnancy (TOP) for central nervous system (CNS) defects. Study design: This is a secondary analysis of a 10 years prospective observational study. Cases of TOP < 23 weeks for CNS malformation that had undergone neurosonography (NSG), iuMRI, pmMRI and autopsy were included. The agreement between iuMRI and pmMRI was calculated. The autopsy represented the gold-standard. Results: Overall, 143 TOPs for fetal congenital anomaly underwent the post-mortem diagnostic protocol. Of these, 31 cases underwent iuMRI and pmMRI for CNS abnormality. Three cases were excluded due to brain autolysis at autopsy. Corpus callosum defects were the most represented (16/28; 57 %). In only one case of posterior fossa defect, pmMRI identified the presence of vermian hypoplasia not diagnosed at iuMRI. In 2 cases (7%), iuMRI added clinically relevant additional findings to NSG, that were posteriorly confirmed by pmMRI. Conclusions: The study shows that, at 19–23 weeks and for CNS defects, limiting factors that might influence the performance of iuMRI have little influence on iuMRI accuracy. This finding is particularly important for professionals who work in countries with legal bound for TOP in the early second trimester.