Cerebral palsy rates by birth weight, gestation and severity in North of England, 1991-2000 singleton births.

To investigate changes in rates of cerebral palsy (CP) by birth weight, gestational age, severity of disability, clinical subtype and maternal age in the North of England, 1991-2000. Data on 908 cases of CP (816 singletons, 92 multiples) were analysed from the prospective population-based North of England Collaborative Cerebral Palsy Survey. Severity of disability, measured as a Lifestyle Assessment Score (LAS), was derived from the lifestyle assessment questionnaire. CP rates by birth weight, gestational age, birth weight standardised for gestational age and sex, severity of disability and maternal age were compared between 1991-1995 and 1996-2000 using rate ratios (RR). The prevalence of CP in singletons was 2.46 (95% CI 2.29 to 2.63) per 1000 neonatal survivors compared to 11.06 per 1000 (95% CI 8.81 to 13.3) in multiples (RR 4.49, 95% CI 3.62 to 5.57), with no significant change between quinquennia. The singleton CP rates were higher for lower birth weight groups than birth weight ≥2500 g; and there were no significant changes for any birth weight group between quinquennia. There were also no changes in rates of more severe disability (LAS≥30%) by birth weight, gestation or clinical subtype. For preterm and term births the patterns of Z-score of birth weight-for-gestation are similar, with CP rates increasing as Z-score deviates from the optimal weight-for-gestation, which is about 1 SD above the mean. In contrast to increasing rates in previous years, rates of CP and more severe CP were stable by birth weight, gestational age and clinical subtype for 1991-2000.