The normal fetal lateral ventricular diameter remains stable at 10 mm over gestation. Mild ventriculomegaly, defined as a lateral ventricular diameter of >or=10 mm but <or=15 mm or a choroid-lateral ventricular separation >or=3 mm but <or=8 mm occurs bilaterally in 0.15-0.7% of fetuses and unilaterally in 0.07% of pregnancies. This finding is associated with an increased risk of fetal chromosomal abnormalities, congenital anomalies and infections, syndromes, perinatal death, and childhood developmental delays. Prenatal evaluation includes targeted sonographic examination for central nervous system and extra-central nervous system abnormalities, and diagnostic amniocentesis for chromosomal analysis and infectious disease studies. Individualized patient counseling is based on these test results. Optimal postnatal care involves appropriate pediatric neurologic and developmental specialists.