Is arterial hypertension crucial for the development of cerebral haemorrhage in premature infants?

Computerised tomography has revealed that more than 40% of premature neonates (birth weight smaller than 1500 g) have cerebral bleeds in the first 3 or 4 days of extrauterine life. Injection studies done at necropsy have shown that they usually originate in the capillaries of the germinal matrix. It is suggested that premature neonates are hypertensive when their blood-pressure is compared with that in utero, and that events that lead to further rises in pressure are common. Their capillaries are not protected against rises in arterial pressure because autoregulation is impaired. Furthermore, the capillaries in the germinal matrix are not supported by firm glial structures. Arterial pressure rises are therefore likely to be responsible for germinal matrix haemorrhage in the premature neonate, and the risk of haemorrhage probably diminishes as autoregulation of cerebral blood-flow is restored a few days after birth.