title: Maternal parity and the risk of congenital heart defects in offspring: a dose-response meta-analysis of epidemiological observational studies.
abstract: BACKGROUND
  Epidemiological studies have reported conflicting results regarding maternal parity and the risk of congenital heart defects (CHDs). However, a meta-analysis of the association between maternal parity and CHDs in offspring has not been conducted.
  
  
  METHODS
  We searched MEDLINE and EMBASE for articles catalogued between their inception and March 8, 2014; we identified relevant published studies that assessed the association between maternal parity and CHD risk. Two authors independently assessed the eligibility of the retrieved articles and extracted data from them. Study-specific relative risk estimates were pooled by random-effects or fixed-effects models. From the 11272 references, a total of 16 case-control studies and 3 cohort studies were enrolled in this meta-analysis.
  
  
  RESULTS
  The overall relative risk of CHD in parous versus nulliparous women was 1.01 (95% CI, 0.97-1.06; Q = 32.34; P = 0.006; I2 = 53.6%). Furthermore, we observed a significant association between the highest versus lowest parity number, with an overall RR = 1.20 (95% CI, 1.10-1.31; (Q = 74.61, P<0.001, I2 = 82.6%). A dose-response analysis also indicated a positive effect of maternal parity on CHD risk, and the overall increase in relative risk per one live birth was 1.06 (95% CI, 1.02-1.09); Q = 68.09; P<0.001; I2 = 80.9%). We conducted stratified and meta-regression analyses to identify the origin of the heterogeneity among studies. A Galbraith plot was created to graphically assess the sources of heterogeneity.
  
  
  CONCLUSIONS
  In summary, this meta-analysis provided a robust estimate of the positive association between maternal parity and risk of CHD.
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Di
authors.initials: D
authors.lastname: Yu
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Atherosclerosis Research Center, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Tong
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Min
authors.initials: M
authors.lastname: Da
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Shutong
authors.initials: S
authors.lastname: Shen
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Changfeng
authors.initials: C
authors.lastname: Fan
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Song
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Cardiothoracic Surgery, The Affiliated Children's Hospital of Nanjing Medical University, Nanjing, Jiangsu, China.
authors.forename: Xuming
authors.initials: X
authors.lastname: Mo
mesh_terms: D016021:Epidemiologic Studies; D005260:Female; D006330:Heart Defects, Congenital / Q000453:epidemiology*; D006801:Humans; D010298:Parity; D012307:Risk Factors