This case demonstrates the utility of fetal MRI in characterization and prognostication of intracranial abnormalities detected sonographically.  Routine 2nd trimester ultrasound found unilateral ventricular enlargement. However fetal neurosonography is limited in assessment of grey matter structures and sulcation.  Additional findings on the subsequent MRI included overall increased size of the right hemisphere, lateral ventricle and calvaria with suspected polymicrogyria and grey matter heterotopia.  The features are in keeping with hemimegalencephaly, which carries a poor neurological prognosis.