Longitudinal changes in bone density in relation to oral contraceptive use.

The primary aim of this 36-month prospective cohort study was to evaluate the association between use of oral contraceptives (OCs) and bone mineral density in reproductive-age women. The 36-month bone density (g/cm2) at the spine, hip and whole body and percent change from baseline (measured at 6-month intervals) were evaluated among 245 women 18-39 years of age; 89 were using OCs (median duration: 3.7 years at study entry) and 156 were not using any hormonal contraception. Before and after adjustment for covariates (baseline bone density, age, race, ever pregnant, exercise, body mass and calcium intake), women using OCs did not differ significantly from comparison women in percent change in bone density over 36 months or in absolute bone density at 36 months. All p-values for between-group differences were >0.55. In conclusion, within the limitations of this study, OCs did not appear to impact bone density over time in this cohort of reproductive-age women.