IUDs, Implants More Effective Than Pills, Rings, and Patches

Ricki Lewis, PhD

May 23, 2012

May 23, 2012 — Long-acting reversible contraception methods (intrauterine devices [IUDs] and implants) were more than 20 times more successful in preventing pregnancy than other frequently used methods (oral contraceptives, vaginal ring, transdermal patch, and depot medroxyprogesterone acetate [DMPA] injection), according to results from a large, prospective cohort study. The results are published in the May 24 issue of the New England Journal of Medicine.

All contraceptive methods are highly effective, according to authors Brooke Winner, MD, from the Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri, and colleagues, but they must be used properly and consistently to avoid pregnancy. In the United States, about 50% of all pregnancies are unplanned; that translates into roughly 3 million unplanned pregnancies annually. Approximately half of unplanned pregnancies in the United States are the result of contraceptive failure, which in turn is a result of incorrect or inconsistent use; the other half are a result of nonuse of contraception. Unintended pregnancy is more common in the United States than in many other developed countries, and results in 1.2 million abortions nationally each year.

Birth control pills are much more popular than IUDs; one reason for this is economics: the longer-acting devices may cost more than $500, as explained in a news release about the current trial. An advantage of IUDs and implants, in contrast, is ease of compliance. "Once these methods are placed, women don't need to worry about remembering to take them, or about their insurance changing or having issues getting to the pharmacy," Alison Edelman, MD, MPH, an obstetrician/gynecologist at Oregon Health & Science University in Portland, told Medscape Medical News. Dr. Edelman was not involved in the study.

The researchers offered participants the choice of contraceptive method (pill, ring, patch, DMPA, IUD, or implant) to 7486 women at risk for unintended pregnancy, aged 14 to 45 years, at no cost. The women received counseling about effectiveness, risk, benefits, and adverse effects of each method and were allowed to switch methods during the study. They were told that IUDs and implants are the most effective methods for preventing pregnancy.

The investigators interviewed participants by telephone at 3 months and 6 months and at 6-month intervals for the 3 years of the study, following up reports of missed periods with urine pregnancy tests at the Washington University facility. The participants were given $10 gift cards for each completed interview follow-up. Data were also collected from participating pharmacies and from the participants' logs of contraceptive methods. The prospective design avoided recall bias.

The researchers found 334 unintended pregnancies among the 7486 participants. The failure rate for pills, ring, or patch was 4.55 per 100 participant-years (133 pregnancies) compared with 0.27 (21 pregnancies) among those using IUDs or implants (hazard ratio, 21.84; 95% confidence interval, 13.67 - 34.88, adjusting for history, age, and educational level).

Contraception failure inversely correlated to age. Participants younger than 21 years who used pills, patch, or ring conceived without intending to at nearly twice the rate as older participants who used these methods (hazard ratio after adjustment for educational level and history of unintended pregnancy, 1.9; 95% confidence interval, 1.2 - 2.8; P = .02). However, no age effect emerged among women using IUD, implant, or DMPA injection.

The researchers conclude that "participants using oral contraceptive pills, a transdermal patch, or a vaginal ring had a risk of contraceptive failure that was 20 times as high as the risk among those using long-acting reversible contraception." These findings are similar to those of other studies that were retrospective.

When cost was removed from the decision process for contraception, 75% of the women chose IUDs and implants, a large increase over the 5.5% of women in the United States who use these more invasive and expensive methods. Women choosing IUDs and implants in the study were more likely to be older, have public health insurance, and have higher parity than women who chose the other methods. The women who chose pills, ring, or patch were more likely to be nulliparous and to have private health insurance.

Limitations of the study include the nonrandomized design and selection bias for women willing to switch or begin birth control method. The freedom to choose a method at no cost may have boosted compliance, but this was likely balanced by the fact that the study population was at higher risk for unintended pregnancy, the researchers write.

The study's findings echo experience: "A resurgence in IUD use is already occurring. IUDs have been very popular due to their high efficacy rates and beneficial effects of minimizing menstrual bleeding," Beatrice Tsao, MD, an obstetrician/gynecologist at CareNet Medical Group in Schenectady, New York, told Medscape Medical News.

The study was funded by the Susan Thompson Buffet Foundation. One coauthor provided expert testimony for the defense in a case regarding thromboembolism with contraceptive vaginal ring use and received lecture fees from Omnia Education, and his institution received fees from Merck as an etonogestrel-implant trainer and royalties from Lippincott. One coauthor received lecture fees from Bayer HealthCare Pharmaceuticals. Dr. Edelman has assisted with advisory boards and training programs for Agile, Bayer, and Merck. The other authors and Dr. Tsao have disclosed no relevant financial relationships.

N Engl J Med. 2012;366:1998-2007. Abstract

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