Trends in perinatal mortality and cerebral palsy in Western Australia, 1967 to 1985.

OBJECTIVE To analyse the trends in stillbirths, neonatal deaths, and cerebral palsy in all infants born in Western Australia from 1967 to 1985. To relate these trends to changes in perinatal care, particularly in relation to avoidance of intrapartum asphyxia in term infants and the increased survival of low birthweight infants. DESIGN Descriptive epidemiological study calculating population rates for perinatal deaths and cerebral palsy according to year of birth and birth weight. SETTING Western Australia. SUBJECTS All infants born after 20 weeks' gestation or weighing at least 400 g (live and stillborn). MAIN OUTCOME MEASURES Stillbirths, neonatal deaths (from perinatal death certificates), and cerebral palsy (from a population based register). RESULTS Overall stillbirth rates fell from 12.1/1000 total births in 1967-70 to 8.1 in 1983-5. Early neonatal mortality fell from 13.0/1000 live births to 4.4 over the same period whereas total cerebral palsy rates remained at around 2-2.5/1000 live births. Death rates fell in all birth weight categories, particularly in low birthweight infants between 1975 and 1985, the period when birthweight data were available. In contrast, cerebral palsy rates in infants under 1500 g rose significantly over this period (from 12.1 in 1968 to 64.9 in 1985). The rise was seen in all spastic categories, including severely and multiply handicapped children. CONCLUSIONS Large increases in the use of interventions aimed at reducing birth asphyxia and handicaps had not (by 1985) resulted in lower rates of cerebral palsy. This suggests that birth asphyxia is not a major cause. The increased survival of low birthweight infants has resulted in more cerebral palsy in this group, due either to postnatal complications of immaturity or prenatal damage to the fetal brain. These findings have implications for planning perinatal care and for litigation for putative obstetric malpractice in cerebral palsy cases.