Birth weight as a risk factor for breast cancer: a meta-analysis of 18 epidemiological studies

J Womens Health (Larchmt). 2009 Aug;18(8):1169-78. doi: 10.1089/jwh.2008.1034.


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.

Publication types

  • Meta-Analysis
  • Review

MeSH terms

  • Adult
  • Birth Weight*
  • Breast Neoplasms / epidemiology*
  • Causality
  • Confidence Intervals
  • Epidemiologic Studies
  • Female
  • Humans
  • Middle Aged
  • Models, Statistical
  • Monte Carlo Method
  • Odds Ratio
  • Risk Factors
  • United States
  • Women's Health*