Cerebral and renal artery blood flow velocity before and after birth.

Objective: To document perinatal changes in cerebral and renal artery haemodynamics in premature growth-retarded and normal term infants.
Design: Longitudinal study of individual infants. Doppler ultrasound measurements of blood flow velocity (BFV) in the middle cerebral and renal arteries were obtained before delivery, soon after delivery and during the first week of postnatal life.
Setting: Teaching hospital obstetric and neonatal units.
Subjects: 13 severely growth retarded infants born at 28-36 weeks gestation, and eight normally grown infants born at term.
Results: In both groups, BFV in the cerebral artery was significantly lower in the first few hours after birth than in fetal life, but subsequently increased to reach pre-delivery values by the end of the first week. In contrast, BFV in the renal artery during the first postnatal day was not significantly different from fetal values, but it also increased during the subsequent week. In six of the preterm growth-retarded infants, fetal blood gases were measured in samples obtained by cordocentesis, and in these cases an increase in blood oxygen content at birth was documented.
Conclusions: Cerebral artery BFV falls at birth and is relatively low during the time that premature infants are at the greatest risk of developing periventricular haemorrhage.