title: Risk factors associated with late preterm births in the underdeveloped region of China: A cohort study and systematic review.
abstract: OBJECTIVE
  To determine factors associated with late preterm births in an underdeveloped region of China, and search for relevant reports in other underdeveloped regions by a systematic review.
  
  
  METHODS
  Data of births occurring between January 2004 and December 2008 from eight hospitals in Western Sichuan Province, China, were analyzed. Late preterm birth was defined as delivery at 34-36 6/7 weeks' gestation. Medline, Cochrane Library, and Google Scholar were searched for studies which reported the risk factors of late preterm births in undeveloped regions until January 31, 2014.
  
  
  RESULTS
  During the study period there were 4711 late preterm births and 54,574 term births. The odds ratios (ORs) for a late preterm birth of mothers < 20 years and ≥ 35 years of age were 3.813 [95% confidence interval (CI): 3.256-4.465] and 1.872 (95% CI: 1.677-2.090), respectively, as compared with an age of 20-34.9 years. Mothers who received prenatal care were less likely (OR = 0.623, 95% CI: 0.582-0.667) and those with a multiple gestation were more likely (OR = 9.346, 95% CI: 7.813, 11.236) to have a late preterm birth. The systematic review found that the incidence of late preterm births ranged from 4.4% to 16%, and the most prominent risk factors were eclampsia, preeclampsia, placenta previa, placental abruption, and twin pregnancy.
  
  
  CONCLUSIONS
  A number of factors are associated with late preterm births, and the incidence in underdeveloped regions is high. The inconsistent results between our study and previous reports indicate more attention towards preventing late preterm births in undeveloped regions is needed.
authors.affiliation: Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, China.
authors.forename: Liqun
authors.initials: L
authors.lastname: Lu
authors.affiliation: Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Qu
authors.affiliation: Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Pediatrics, West China Second University Hospital, Sichuan University, Chengdu, China. Electronic address: dezhi.mu@ucsf.edu.
authors.forename: Dezhi
authors.initials: D
authors.lastname: Mu
mesh_terms: D000328:Adult; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D036861:Delivery, Obstetric; D003906:Developing Countries; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D011272:Pregnancy, Multiple; D047928:Premature Birth / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
keywords: China; late preterm birth; literature review; risk factor; underdeveloped