title: Cerebral palsy and multiple births in China.
abstract: BACKGROUND
  A population-based study on prevalence of cerebral palsy in multiple births has not been carried out in China. The purpose of this paper was to determine the prevalence of cerebral palsy in multiple births and to explore the influence of multiple pregnancy on cerebral palsy after controlling for birthweight.
  
  
  METHODS
  A cross-sectional study of cerebral palsy was carried out among 388,192 children aged <7 years in seven cities of Jiangsu province in China. Information about birthweight and plurality was obtained from routine health care records. Pediatricians at city level diagnosed all cases. All the doctors involved had taken part in a training programme held by Beijing Medical University. Stratified analysis by birthweight and its standard normal deviate was employed to compare the prevalence of cerebral palsy in multiples and singletons.
  
  
  RESULTS
  The prevalence of cerebral palsy for children aged <7 years in multiples was 9.7 per 1000 children (95% confidence interval [CI]: 6.5-14.0), which was 6.5 times that in singletons (95% CI: 4.4-9.3). The overall neonatal mortality rate was 60.9 per 1000 liveborn multiples, being highest (944.4 per 1000) in the 500-999 g birthweight groups. Most liveborn multiples weighing <1500 g at birth probably died from diseases related to very low birthweight prior to this study. The prevalence of cerebral palsy in multiple births was likely to be higher than that reported in developed countries for children weighing 1500-2499 g even though our data were from a cross-sectional study. When stratified by birthweight, the prevalence of cerebral palsy in multiples weighing <2500 g had tended to be lower than that of singletons in the same birthweight group. In contrast, in normal birthweight categories multiple births had a higher prevalence of cerebral palsy than singletons. When stratified by birthweight normal deviate, the prevalence of cerebral palsy in multiple births was uniformly higher than that in singletons in all birthweight strata and the prevalence of cerebral palsy among multiples appeared to be augmented as birthweight increased.
  
  
  CONCLUSIONS
  The prevalence of cerebral palsy in multiples, 9.7 per 1000 children, is 6.5 times that in singletons. Survival of low birthweight infants is lower in China than in developed countries and survival quality of Chinese children weighing 1500-2499 g needs to be further improved. In terms of birthweight multiples and singletons may be heterogeneous. It might be difficult to directly use actual birthweight specific prevalence to compare the prevalence of cerebral palsy in multiples and singletons. Birthweight normal deviate specific prevalence of cerebral palsy suggests that multiple pregnancy is an independent risk factor for cerebral palsy in all birthweight groups. Multiples are in adverse circumstances very early in gestation and as the foetus matures the risk of cerebral palsy increases.
authors.affiliation: National Center for Maternal and Infant Health, Beijing Medical University, People's Republic of China. Liujm@ncmih.bjmu.edu.cn
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: Z
authors.initials: Z
authors.lastname: Li
authors.forename: Q
authors.initials: Q
authors.lastname: Lin
authors.forename: P
authors.initials: P
authors.lastname: Zhao
authors.forename: F
authors.initials: F
authors.lastname: Zhao
authors.forename: S
authors.initials: S
authors.lastname: Hong
authors.forename: S
authors.initials: S
authors.lastname: Li
mesh_terms: D001724:Birth Weight; D002547:Cerebral Palsy / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007226:Infant Mortality / Q000639:trends; D007231:Infant, Newborn; D009099:Multiple Birth Offspring / Q000706:statistics & numerical data*; D011159:Population Surveillance; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors