New study eyes link to DMPA use, STD risk
Findings from a just-published study indicate that women who use the contraceptive injection depot medroxyprogesterone acetate (DMPA, marketed as Depo-Provera, Pfizer, New York City) appear to have a threefold increased risk of acquiring chlamydia and gonorrhea when compared to women not using a hormonal contraceptive.1
Researchers involved in the prospective cohort study analyzed results from 819 women from two Baltimore-area clinics who were allowed to choose a combined oral contraceptive (OC), DMPA, or a nonhormonal contraceptive. Most of the women (77%) were single and nulliparous; about half (52%) were white, while 43% were African American. After enrolling in the study, women were tested for chlamydial and gonococcal infection after three, six, and 12 months.
The issue is whether DMPA increases a woman’s risk of sexually transmitted disease (STD), or are the women who choose DMPA are more likely to be at risk for STDs, says Susan Wysocki, RNC, NP, president and chief executive officer of the Washington, DC-based National Association of Nurse Practitioners in Women’s Health. The study was not a randomized trial; women chose on their method on their own, Wysocki points out.
Clinicians need to keep in mind that while the newly published study is well designed and carefully executed, it is an observational study, advises James Trussell, PhD, professor of economics and public affairs and director of the Office of Population Research at Princeton (NJ) University.
"What this observational study shows is the users of DMPA appear to be at increased risk of acquiring sexually transmitted cervical infections and not that use of DMPA appears to increase that risk," he notes.
If investigators could confidently control for all issues in all behaviors that impact risk of STD acquisition, then the findings of an observational study may well be valid, agrees Andrew Kaunitz, MD, professor and assistant chair in the obstetrics and gynecology department at the University of Florida Health Science Center/Jacksonville. "However, as we have learned from the Women’s Health Initiative [WHI], that even in the best-done observational studies, there may be important areas that the study is not able to adequately control for, and I am concerned that may be the case here," he says.
Women in the study were not randomized as to their contraceptive method, notes Kaunitz. There is a possibility that women who chose DMPA were different in some ways from the control group, he notes.
The new research underscores an important message for all users of hormonal contraceptives: If women are not in a mutually monogamous relationship with an uninfected partner, they should limit their number of sexual partners and use condoms correctly and consistently every time they have intercourse.
Family planning involves careful counseling and education in pairing method with user so that women make the best choice that most likely will result in contraceptive success, says Kaunitz.
"DMPA certainly fits that bill for many women, particularly younger women who have difficulty achieving contraceptive success with daily methods," he observes. "The take-home message from a study like this is that hormonal methods may not prevent acquisition of cervical STDs, and for women at risk, we need to continue to reinforce that message about safe sex and consistent condom use."
1. Morrison CS, Bright P, Wong EL, et al. Hormonal contraceptive use, cervical ectopy, and the acquisition of cervical infections. Sex Trans Dis 2004; 31:561-567.