Clinical Reasoning: Ventriculomegaly detected on 20-week anatomic fetal ultrasound

A 23-year-old G1P0 woman was referred for fetal MRI after her 20-week anatomic fetal ultrasound demonstrated cerebral ventriculomegaly. Her pregnancy to date had been uncomplicated without notable fevers, illnesses, or need for medications aside from prenatal vitamins. The fetal MRI obtained at 24 weeks gestation demonstrated a phenotypically male fetus with severely dilated lateral ventricles measuring up to 30 mm with marked thinning of the cortical mantle, aqueductal stenosis, diencephalic fusion, and brainstem dysplasia (figure, A and B).