title: Breast-feeding and the onset of rheumatoid arthritis.
abstract: OBJECTIVE
  In a recent study we demonstrated that the postpartum period, particularly after the first pregnancy, is a time of increased risk for the development of rheumatoid arthritis (RA). The present study was undertaken to investigate whether this risk might be explained by breast-feeding.
  
  
  METHODS
  Through a nationwide media campaign, we identified 187 women who had developed RA within 12 months of a pregnancy, and we compared their breast-feeding histories with those of 149 similarly aged women chosen from the patient registers of a nationwide group of general practitioners.
  
  
  RESULTS
  In all, 88 of the women with RA developed the disease after their first pregnancy. Eighty-one percent of these 88 women had breast-fed. This was higher than the breast-feeding prevalence of 50% in the 129 controls whose first pregnancy had resulted in a live birth (adjusted odds ratio [OR] 5.4, 95% confidence interval 2.5-11.4). There was a smaller increased risk of breast-feeding after a second pregnancy in the RA cases (OR 2.0) and no increase after a third pregnancy (OR 0.6). The increase in risk was greatest in those cases whose disease was erosive and who were rheumatoid factor positive.
  
  
  CONCLUSIONS
  In a small group of susceptible women, exposure to breast-feeding after the first pregnancy is associated with a significant increase in risk for RA development. We postulate that this may reflect hormonal influences, specifically the high level of the proinflammatory hormone prolactin.
authors.affiliation: Arthritis and Rheumatism Council, Epidemiology Research Unit, Manchester University Medical School, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Brennan
authors.forename: A
authors.initials: A
authors.lastname: Silman
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000209:etiology*; D001942:Breast Feeding; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D010298:Parity; D012307:Risk Factors