title: Prenatal care in combination with maternal educational level has a synergetic effect on the risk of neonatal low birth weight: new findings in a retrospective cohort study in Kunshan City, China.
abstract: OBJECTIVE
  To investigate the dose-response relationship and synergetic effect of the maternal educational level and two measures of prenatal care on neonatal low birth weight (LBW) risk.
  
  
  METHODS
  Data were derived from the Perinatal Health Care Surveillance System (PHCSS) from January 2001 to September 2009 in Kunshan City, Jiangsu province, eastern China, which included data on 31412 women with a normal birth weight delivery and 640 women with a LBW delivery. Logistic modelling was performed to estimate the association including the joint effects with odds ratio (OR) and 95% confidence interval (CI) between the prenatal care measures and LBW risk after adjusting for the potential confounders. The dose-response relationship between the number of prenatal care visits and the risk of LBW was investigated by modeling the quantitative exposure with restricted cubic splines (RCS).
  
  
  RESULTS
  There was a significant synergetic effect on the LBW risk between maternal educational attainment and the number of prenatal care visits (χ(2) = 4.98, P = 0.0257), whereas no significant maternal educational attainment interaction was found with the week of initiation of prenatal care after adjusting for relevant confounding factors (χ(2) = 2.04, P = 0.1530), and the LBW risk displayed a 'U-shape' curve tendency among the different number of prenatal care visits (P for nonlinearity = 0.0002) using RCS. In particular, the ORs were approaching the curve's bottom when the women had 9 or 10 prenatal care visits. Comparing with 5 prenatal care visits, the ORs and 95%CI of LBW risk for 7, 9, 11 and ≥ 13 visits were 0.92 (0.82-1.03), 0.50 (0.38-0.66), 0.62 (0.47-0.82), and 0.99 (0.61-1.60), respectively.
  
  
  CONCLUSIONS
  Our findings suggest that appropriate prenatal care, in combination with a higher maternal educational level, can produce a protective interaction effect on LBW risk. Reasonable health resource assignment for different social statuses should be taken into account by policy-makers in developing countries.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Medical College of Soochow University, Suzhou, Jiangsu, China.
authors.forename: Lin-Lin
authors.initials: LL
authors.lastname: Dai
authors.affiliation: Kunshan first people's Hospital, Kunshan, Suzhou, Jiangsu, China.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Mao
authors.affiliation: Kunshan fourth people's Hospital, Kunshan, Suzhou, Jiangsu, China.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Luo
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Medical College of Soochow University, Suzhou, Jiangsu, China.
authors.forename: Yue-Ping
authors.initials: YP
authors.lastname: Shen
mesh_terms: D000328:Adult; D002681:China; D004522:Educational Status; D005260:Female; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016015:Logistic Models; D016017:Odds Ratio; D009819:Office Visits / Q000706:statistics & numerical data*; D011247:Pregnancy; D011295:Prenatal Care / Q000523:psychology / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors