title: Birth weight as a risk factor for breast cancer: a meta-analysis of 18 epidemiological studies.
abstract: BACKGROUND
  Birth weight has been identified as a birth-related factor associated with the risk of breast cancer. However, the evidence is inconsistent.
  
  
  METHODS
  To investigate the association between birth weight and breast cancer, we conducted a meta-analysis of published studies between 1996 and 2008. Eighteen studies encompassing 16,424 breast cancer cases were included in the meta-analysis. Data were combined using a fixed-effect or random-effect model depending on the heterogeneity across studies.
  
  
  RESULTS
  Women with their own birth weight >4000 g or 8.5 lb had a higher risk for developing breast cancer than those with birth weight <2500 g or 3000 g (OR = 1.20, 95% CI 1.08, 1.34). Findings were also consistent with a dose-response pattern effect. The summary effect estimate for breast cancer risk per 1 kg increase in birth weight was statistically significant (random effects OR = 1.07, 95% CI 1.02, 1.12).
  
  
  CONCLUSIONS
  Although these results provided no evidence indicating whether birth weight is more strongly related to early-onset than to later-onset breast cancer, our findings suggest an association between birth weight and breast cancer. The underlying biological mechanism relating to this phenomenon needs additional study.
authors.affiliation: Department of Epidemiology & Biostatistics, College of Public Health and Health Professions, University of Florida, Gainesville, FL 32610-0231, USA. xhxu@phhp.ufl.edu
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Xu
authors.forename: Amy B
authors.initials: AB
authors.lastname: Dailey
authors.forename: Mary
authors.initials: M
authors.lastname: Peoples-Sheps
authors.forename: Evelyn O
authors.initials: EO
authors.lastname: Talbott
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Roth
mesh_terms: D000328:Adult; D001724:Birth Weight; D001943:Breast Neoplasms / Q000453:epidemiology*; D015984:Causality; D016001:Confidence Intervals; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D015233:Models, Statistical; D009010:Monte Carlo Method; D016017:Odds Ratio; D012307:Risk Factors; D014481:United States; D016387:Women's Health