In the population-based Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA) study, women with a history of oral contraceptive (OC) use had a decreased risk of developing anti-citrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA) compared with women who had never used OCs (OR 0.87, 95%CI 0.78–0.97). The risk of ACPA-positive RA among smokers was higher in those who had never used OCs than in those who had. The study could not confirm an association between breastfeeding and a decreased risk of either ACPA-positive or ACPA-negative RA.