OBJECTIVE To evaluate fetuses with sonographically suspected central nervous system anomalies to determine the frequency with which obstetric magnetic resonance (MR) imaging adds clinically useful information to that provided by ultrasonography (US). METHODS US and MR images and diagnoses in 18 pregnant women were reviewed and compared by two radiologists. Postnatal physical examination and imaging findings and fetal autopsy results were standards. Referring physicians were questioned as to how the additional information provided by MR imaging changed patient counseling. RESULTS In 10 (55%) patients, MR imaging demonstrated 11 additional findings. These findings were agenesis of the corpus callosum (n = 4), cerebellar hypoplasia (n = 2), cortical cleft (n = 2), polymicrogyria (n = 1), porencephaly (n = 1), and partial agenesis of the septi pellucidi (n = 1). In seven (39%) patients, additional information provided by MR imaging altered counseling. In one case of suspected agenesis of the corpus callosum, diagnosis at MR imaging was at least partially incorrect. CONCLUSIONS US and MR imaging are complementary imaging methods in the evaluation of high-risk pregnancy. When a central nervous system anomaly is suspected at US, MR imaging may demonstrate additional findings that can alter patient counseling.