Contraceptive use and fracture risk in active-duty females - A case control study

To determine a possible association of hormonal contraception use with military stress fractures given impact of readiness and hypothesized fracture risk with continuous contraceptive use while deployed.

This IRB approved case-control study used incidence density sampling to assess associations between hormonal contraceptives and stress fracture. Up to four controls were matched to each case of stress fracture based on race/ethnicity, service branch, age, and time in service. Cases with <4 months of service were excluded. Crude and adjusted incidence rate ratios and 95% confidence intervals (CIs) were calculated to estimate effects of hormonal contraceptive use to incident stress fracture diagnosis. Intrauterine devices (IUDs), implants, and injectables were analyzed separately and oral contraceptives (OC), patches, and vaginal rings were analyzed combined given their similar mechanisms.

Cases (n = 1689) were more likely to be enlisted, vitamin D deficient, obese, and have a history of bone disease. Before adjustment, no hormonal contraceptives were associated with increased risk of fracture. After adjustment for obesity and rank, only the combination of OC/patches/vaginal rings demonstrated a statistically significant association with stress fracture after 2-3 years of use (IRR 2.17, 95% CI 1.10-4.28, p value 0.03).

Our study suggests limited or no associations between recent hormonal contraceptive use and increased risk for stress fracture. This potential association should be investigated further.

This study finds that hormonal contraceptives are not associated with an increased risk of stress fracture and supports knowledge of hormonal effects on bone and prescribing considerations in highly active women.