To explore the sonographic features of fetal hemimegalencephaly (HME) in the second trimester of pregnancy.

The prenatal ultrasonograms of 4 fetuses, which were diagnosed as having HME at Shenzhen Maternal and Child Health Hospital of Southern Medical University from January 2008 to October 2020, were retrospectively reviewed.

The prenatal ultrasonograms of the 4 HME fetuses were characterized as hemisphere asymmetry, shift in midline structure, uneven cortical thickness, and sylvian fissure asymmetry. Among them, 1 case had severe hydrocephalus in the lateral ventricle, 1 had corpus callosum hypoplasia, optic septum hypoplasia, cerebellar hemisphere and vermis hypoplasia, bilateral hydrocephalus, and nasal bone hypoplasia, and 1 had craniocerebral midline cyst, which was consistent with the ultrasound features reported in the literature. All 4 cases were confirmed by MRI.

HME is a rare congenital developmental malformation of the central system with typical prenatal ultrasound findings. Timely prenatal ultrasound screening can provide more information for prenatal counseling and early intervention for pregnant mothers.