Bone mineral density in women using depot medroxyprogesterone acetate for contraception

Objective: To evaluate the possible effects of depot medroxyprogesterone ac etate injectable contraception on bone mineral density in reproductive-age women. Methods: We conducted a population-based cross-sectional comparison of bone mineral density levels in women using depot medroxyprogesterone acetate co ntraception and in women of similar age not using this method. The study re cruited 457 nonpregnant women aged 18-39 years who were enrollees of a Wash ington state health maintenance organization. One hundred eighty-three wome n were receiving injections and 274 were not. Bone mineral density at sever al anatomic sites (spine, femoral neck, greater trochanter, and whole body) was measured using dual-energy x-ray absorptiometry. Data on other factors potentially related to bone density were collected through questionnaire a nd examination. Results: Overall, age-adjusted mean bone density levels were lower for user s of this method than for nonusers at all anatomic sites: The mean differen ce was 2.5% for the spine (P = .03) and 2.2% for the femoral neck (P = .12) . Exposure to depot medroxyprogesterone acetate continued to be significant ly (P < .01) associated with decreased bone density at the femoral neck, sp ine, and trochanter after multivariate adjustment for other risk factors re lated to bone density. Age-specific comparisons indicated that the major di fferences in bone density between users and nonusers occurred in the younge st age group (women 18-21 years); the mean femoral neck bone density was 10 .5% lower (P < .01) for the exposed women, and differences were consistent (P < .01) across all anatomic sites. We also noted a significant dose-respo nse relation between longer use of depot medroxyprogesterone acetate and de creased bone density levels in this age group (P < .01 for all sites). Conclusion: These results provide evidence that contraception with depot me droxyprogesterone acetate, particularly long-term use, may adversely affect bone mineral density levels in young women aged 18-21 years. The implicati ons for future bone health need further study. (Obstet Gynecol 1999;93:233- 8. (C) 1999 by The American College of Obstetricians and Gynecologists.).