title: Cerebral palsy: effects of twinning, birthweight, and gestational age.
abstract: OBJECTIVE
  To determine the effects of birthweight and gestational age on the risk of cerebral palsy for multiple and singleton births.
  
  
  METHODS
  Children on the North East Thames Regional Health Authority Interactive Child Health System, born between 1 January 1980 and 31 December 1986, and notified as having cerebral palsy, were included. Cases of postneonatal onset, of known progressive, or non-cerebral pathology and with only mild signs were excluded. Rates and relative risks were calculated using the most complete data, which related to 1985-86, and comprised 102,059 singletons and 2367 twins. Logistic regression was used to examine the associations between being a twin, gestational age, and birthweight.
  
  
  RESULTS
  The crude rate per 1000 survivors at 1 year of age was 1.0 in singletons and 7.4 in twins. The relative risk was greatest in twins weighing more than 2499 g (4.5). However, after adjusting for reduced birthweight of twins it was the relative risk of twins weighing less than 1400 g that was significantly increased. Logistic regression confirmed that lower fetal growth, lower gestational age, and being a twin are all independent risk factors for cerebral palsy.
  
  
  CONCLUSIONS
  The increased risk to twins of cerebral palsy is not entirely explained by their increased risk of prematurity and low birthweight.
authors.affiliation: Department of Epidemiology and Medical Statistics, St Bartholomew's & Royal London School of Medicine, London.
authors.forename: K
authors.initials: K
authors.lastname: Williams
authors.forename: E
authors.initials: E
authors.lastname: Hennessy
authors.forename: E
authors.initials: E
authors.lastname: Alberman
mesh_terms: D001724:Birth Weight; D002547:Cerebral Palsy / Q000453:epidemiology*; D004200:Diseases in Twins / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D012044:Regression Analysis; D012307:Risk Factors