Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.Take Posttest
Intrauterine devices (IUDs) and contraceptive implants were far more effective in preventing unwanted pregnancies than pill, patch, or ring-type birth control products in a large, open-label study.
In a trial involving nearly 7,500 women followed for up to 3 years, unwanted pregnancy rates averaged 4.55 per 100 person-years in those choosing pills, patches, or vaginal rings for contraception, compared with 0.27 per 100 person-years with IUDs or implants (P0.001), according to Jeffrey Piepert, MD, PhD, and colleagues at Washington University in St. Louis.
“Half of all pregnancies in the U.S. are unintended, and half of those result from contraceptive failure,” the researchers wrote in the May 24 issue of the New England Journal of Medicine.
“If more women used the highly effective, long-acting reversible methods, we would expect a decrease in the number of unintended pregnancies, because there would be more women continuing to use contraception,” they said of IUDs or the subdermal hormonal implant.
Their findings came from the Contraceptive CHOICE Project, which enrolled 8,445 sexually active women, including teens as young as 14, in the St. Louis area from August 2007 to September 2011.
They were given a choice of contraceptives that were provided free. Participants could switch methods at any time. Condoms for their male partners could not be used exclusively — their choices were restricted to female contraceptives, although participants were not discouraged from having their partners use condoms.
The specific options were IUDs, the Implanon subdermal etonogestrel implant, depot medroxyprogesterone acetate (DMPA), oral hormonal products, transdermal patches, or a contraceptive vaginal ring.
Follow-up consisted of telephone calls 3 and 6 months after starting in the study and every 6 months afterward. Participants were asked about missed periods and potential pregnancies. Those who said they might be pregnant were encouraged to visit the clinic for testing.
Participants found to be pregnant were asked whether it was intended and what contraceptive they were using at the estimated time of conception.
The first 5,090 participants were followed for 3 years and those enrolled later were tracked for 2 years. The analysis was limited to the first 7,486 meeting the study’s eligibility criteria.
Most participants (5,781) picked the long-acting reversible methods. DMPA was selected by 176, and 1,527 chose pills, patches, or ring (PPR).
Those choosing PPR and the IUD/implant methods were generally similar in socioeconomic characteristics. Relative to those groups, participants who picked DMPA were more likely to be African American, poor, uninsured, and having high school or less education.
On the other hand, the long-acting reversible methods were more popular among participants who reported at least one pregnancy before entering the study (59% versus 49% for DMPA and 29% for PPR).
There were a total of 334 unintended pregnancies reported by all participants in the analysis. Three-year rates were virtually identical among participants using long-acting reversible methods or DMPA (0.9% and 0.7%, respectively). The rate among PPR users was about 10-fold higher at 9.4% (P0.001 relative to the other two groups).
Contraceptive failure rates differed by age among PPR users. Their failure rate was about twice as high in those younger than 21 relatively to older women (hazard ratio 1.9, 95% CI 1.2 to 2.8, after adjustment for education level and history of unintended pregnancy).
Even among the older participants, though, the failure rate of 4.01 per 100 person-years was still substantially higher than with DMPA and the long-acting reversible methods.
In the IUD/implant and DMPA users, there were too few unintended pregnancies for meaningful analysis by age.
Piepert and colleagues suggested that, with few contraindications to IUDs and the subdermal implant, these products are the smart choice for “almost all” sexually active women who don’t want to become pregnant, especially in adolescents, for whom failure of PPR methods is especially common.
Limitations to the study included the nonrandomized, open-label design, and certain characteristics of the study sample. In particular, Piepert and colleagues noted that participants were at high risk for unintended pregnancy and, as a condition of enrollment, were willing to switch contraceptive methods.
The latter could limit the generalizability of results and possibly overestimate contraceptive failure rates relative to the general population.
But the researchers argued that providing the contraceptives at no cost would probably depress the failure rates, so that the biases may cancel each other out.
The study was supported by the Susan Thompson Buffet Foundation.
Piepert reported speaking fees from Merck and Omnia Education, royalties from Lippincott, and payments for consultation and expert testimony on behalf of the defense in litigation involving thromboembolic disorders related to the contraceptive vaginal ring. Another author reported fees from Bayer HealthCare. Other authors declared they had no relevant financial interests.
Primary source: New England Journal of Medicine
Winner B, et al “Effectiveness of long-acting reversible contraception” New Engl J Med 2012; 366: 1998-2007.
John Gever, Senior Editor, has covered biomedicine and medical technology for 30 years. He holds a B.S. from the University of Michigan and an M.S. from Boston University. Now based in Pittsburgh, he is the daily assignment editor for MedPage Today as well as general factotum on the reporting side. Go Pirates/Penguins/Steelers!
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Article source: http://www.medpagetoday.com/OBGYN/Pregnancy/32880