Consequences of birth asphyxia
To investigate the relationship between birth asphyxia and neurological impairment a cohort of 184 infants with a low (≤3) one-minute Apgar score was studied. All were singletons, apparently normally formed, and born at term (≥37 weeks' gestation) in the John Radcliffe Hospital, between January 1984 and September 1985. The 181 cohort survivors were traced at the age of five years; 159 were assessed by a paediatrician on a battery of neurodevelopmental tests, and information about a further eight was obtained from other sources. Three infants in the cohort died neonatally with a diagnosis of birth asphyxia, and three had spastic quadriplegia, profound developmental delay and visual impairment. Examination of the perinatal histories of these six children, including their fetal heart rate patterns in labour and acid-base status at delivery, found convincing evidence of birth asphyxia. Only one other child in the cohort exhibited similar signs of birth asphyxia; he was unimpaired at the age of five. To assess the impact of birth asphyxia on the overall rate of cerebral palsy, all cases of cerebral palsy born to Oxford residents in the study period were identified. Of 30 cases of cerebral palsy, the three identified in the follow-up study were the only ones whose impairment could be attributed to birth asphyxia in a full-term birth. Birth asphyxia therefore accounted for 10% of all cases of cerebral palsy, a fraction that agrees with previous estimates. The frequency of cerebral palsy due to birth asphyxia was estimated as 1 in 3800 full-term livebirths. A detailed analysis of the test scores of the 159 children assessed by the paediatrician failed to show any association between their acid-base values at delivery and test scores, or between their fetal heart rate patterns in labour and test scores. These results conform with the view that birth asphyxia has an "all or nothing" effect, and that it presents as a cluster of abnormal neonatal signs, including persistent cerebral depression, severe acidaemia, neonatal encephalopathy, and multiorgan dysfunction.