title: [Prevalence of preterm birth among singletons in 10 counties (cities) of China, 1993-2005].
abstract: OBJECTIVE
  To describe the secular trends and epidemiological characteristics of preterm birth among singletons in 10 counties (cities) of China during 1993-2005.
  
  
  METHODS
  We analyzed data on 542 923 women (gestational age > or =28 weeks) collected through Perinatal Healthcare Surveillance System established by the Institute of Reproductive and Child Health, Peking University. Chi-square tests were employed to test the differences in prevalence of preterm birth among different groups.
  
  
  RESULTS
  25 784 preterm births were identified, including 1530 stillbirths. Preterm birth rate was 4.75% (95% CI:4.69-4.81) for all births and 4.49% (95% CI:4.44-4.55) for live births. Preterm birth rate declined steadily from 1993 to 2005 and had no significant seasonal variation. Preterm birth rate from the urban areas of the Southern part of the country,was higher than that in the rural areas which was also higher than that seen in the rural areas from the northern part of the country. Relations between women's age at delivery and preterm birth appeared to be U-shaped. Increased preterm birth rates were also observed in women with lower education level,more parities,and previous history of preterm birth or abortion.
  
  
  CONCLUSIONS
  Preterm birth rate decreased steadily from 1993-2005 in 10 counties (cities) but varied by areas of the country.
authors.affiliation: Institute of Reproductive and Child Health, Peking University, Beijing 100083, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
authors.forename: Jian-meng
authors.initials: JM
authors.lastname: Liu
authors.forename: Ying-hui
authors.initials: YH
authors.lastname: Liu
authors.forename: Zhi-wen
authors.initials: ZW
authors.lastname: Li
authors.forename: Rong-wei
authors.initials: RW
authors.lastname: Ye
authors.forename: Jun-chi
authors.initials: JC
authors.lastname: Zheng
authors.forename: Zhu
authors.initials: Z
authors.lastname: Li
mesh_terms: D000328:Adult; D001723:Birth Rate / Q000639:trends*; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D015995:Prevalence; D012424:Rural Population; D014505:Urban Population; D055815:Young Adult