[Hydrocephalus in one twin after massive reverse flow in the umbilical artery in the 2nd trimester].

The case of a twin pregnancy with severe diastolic reverse flow in the umbilical artery of one of the twins at 23 weeks' gestation is reported. After delivery at 29 weeks' gestation, a congenital internal hydrocephalus was diagnosed in this twin. The most probable aetiology is an intrauterine periventricular haemorrhage. The severe diastolic reverse flow in the umbilical artery seems to represent a highly pathological flow pattern of prefinal degree, possibly leading to cerebral defects. The pathophysiology of the Doppler findings and the pathogenesis of the internal hydrocephalus are discussed.