Prenatal, intrapartum and postnatal factors are compared between 15 preterm infants, known to have periventricular leukomalacia (PVL) on ultrasound and 15 infants of similar birthweight and gestation who ultrasonographically showed no evidence of cystic lesions, and who are known to be neurologically normal at follow up. Prenatally, the incidence of antepartum haemorrhage was significantly higher in the PVL group. Intrapartum factors were similar between the two groups but postnatally, the PVL group had significantly lower PaCO2 readings during the first 72 h of life. It is postulated that a severe maternal bleed in late pregnancy and neonatal hypocarbia could significantly decrease cerebral perfusion and cause areas of ischaemia and infarction resulting in periventricular leukomalacia.