The effect of oral contraceptives on bone mass and stress fractures in female runners

Med Sci Sports Exerc. 2007 Sep;39(9):1464-73. doi: 10.1249/mss.0b013e318074e532.


Purpose: To determine the effect of oral contraceptives (OC) on bone mass and stress fracture incidence in young female distance runners.

Methods: One hundred fifty competitive female runners ages 18-26 yr were randomly assigned to OC (30 microg of ethinyl estradiol and 0.3 mg of norgestrel) or control (no intervention) for 2 yr. Bone mineral density (BMD) and content (BMC) were measured yearly by dual x-ray absorptiometry. Stress fractures were confirmed by x-ray, magnetic resonance imaging, or bone scan.

Results: Randomization to OC was unrelated to changes in BMD or BMC in oligo/amenorrheic (N=50) or eumenorrheic runners (N=100). However, treatment-received analyses (which considered actual OC use) showed that oligo/amenorrheic runners who used OC gained about 1% per year in spine BMD (P<0.005) and whole-body BMC (P<0.005), amounts similar to those for runners who regained periods spontaneously and significantly greater than those for runners who remained oligo/amenorrheic (P<0.05). Dietary calcium intake and weight gain independently predicted bone mass gains in oligo/amenorrheic runners. Randomization to OC was not significantly related to stress fracture incidence, but the direction of the effect was protective in both menstrual groups (hazard ratio [95% CI]: 0.57 [0.18, 1.83]), and the effect became stronger in treatment-received analyses. The trial's statistical power was reduced by higher-than-anticipated noncompliance.

Conclusion: OC may reduce the risk for stress fractures in female runners, but our data are inconclusive. Oligo/amenorrheic athletes with low bone mass should be advised to increase dietary calcium and take steps to resume normal menses, including weight gain; they may benefit from OC, but the evidence is inconclusive.

Publication types

  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Amenorrhea / complications
  • Amenorrhea / drug therapy
  • Bone Density / drug effects*
  • Contraceptives, Oral, Hormonal / adverse effects
  • Contraceptives, Oral, Hormonal / therapeutic use*
  • Energy Intake / physiology
  • Female
  • Fractures, Stress / epidemiology
  • Fractures, Stress / etiology
  • Fractures, Stress / prevention & control*
  • Humans
  • Oligomenorrhea / complications
  • Oligomenorrhea / drug therapy
  • Risk Assessment
  • Running / injuries*
  • Running / physiology
  • United States / epidemiology


  • Contraceptives, Oral, Hormonal