Encephalomalacia in surviving twin after single fetal death diagnosed at 18 weeks of gestation in monochorionic twin pregnancy

Objective: Rare disease Background: Single fetal death in monochorionic twin pregnancy may result in poor perinatal outcome of the surviving twin, including neurologic sequelae, other organ injury, and death. In most reported cases of poor perinatal outcome in the surviving twin, monochorionic co-twin death occured after more than 20 weeks of gestation, while few with earlier occurrence have been presented. Case Report: A 28-year-old primigravid woman was referred to our hospital at 18 3/7 weeks of gestation for perinatal management of single fetal death in a monochorionic-diamniotic twin pregnancy. Our first evaluation by ultrasonography revealed a dead twin sized at 16 weeks of gestation, and an alive one with normal size and appearance, together with 1 placenta and 2 amniotic cavities with normal fluid amounts. At 20 3/7 weeks of gestation, ultrasonography showed that the surviving twin had bilateral ventriculomegaly and dilatation all around the subarachnoid cavity despite a normal head size. Fetal magnetic resonance imaging revealed remarkable atrophy of the cerebral cortex. After counseling, the patient and family chose termination of pregnancy, and artificial abortion was performed at 21 weeks of gestation. The aborted fetuses were not anomalous. Autopsy pathological findings confirmed encephalomalacia in the surviving twin. Conclusions: Recent development of imaging device make it possible that several abnormalities in central nervous system can be detected in detail at earlier gestational age. It is important to keep this condition in mind even though single fetal death occurred at early gestational age.