NEW ORLEANS, Louisiana — Long-acting reversible contraceptive methods, such as intrauterine devices (IUDs) and implants, are associated with fewer gaps in contraception than pills, patches, and rings, and reduce the risk for unintended pregnancy, according to a new study.

In fact, researchers report that the women not using long-acting contraceptives had a 7-fold increase in contraceptive gaps, defined as 2 or more weeks without contraception.

"It's obvious that long-acting methods work better, but we didn't know the magnitude of the difference," senior investigator Jeffrey Peipert, MD, told Medscape Medical News before the study results were presented here at the American Congress of Obstetricians and Gynecologists 61st Annual Clinical Meeting.

"What I think has not been well quantified is how many women using nonlong-acting methods experience gaps, or periods of nonuse of at least 2 weeks, even though they are generally considered to be contracepting," explained Sarah Proehl, who presented the findings.

Dr. Peipert's group, from Washington University in St. Louis, Missouri, previously reported an almost 22-fold increase in unintended pregnancies among women who used nonlong-acting methods, such as oral contraceptives, the transdermal patch, the contraceptive vaginal ring, and the depot medroxyprogesterone acetate injection (N Engl J Med. 2012;366:1998-2007).

Now, this new analysis of those data identifies contraceptive gaps as the reason behind this difference.

Unintended Pregnancy

"When you're using nonlong-acting methods, you can have gaps — sometimes consciously and sometimes subconsciously. It's these gaps that explain the difference," Dr. Peipert noted. "Among women with gaps, we found a 20% chance of an unintended pregnancy, compared with 1% to 2% if they didn't have gaps."

The study was a subanalysis of the Contraceptive CHOICE Project, an ongoing prospective study designed to promote the use of long-acting reversible contraceptives and reduce the unintended pregnancy rate.

The study involved 7483 women 14 to 45 years of age. They were provided with contraception, free of charge, for 2 to 3 years, and they completed baseline and follow-up surveys every 3 to 6 months during the study period.

 
Women using birth control methods that require daily, weekly, or monthly action are far more likely to have gaps in their contraceptive protection.
 

Participants received counseling on the effectiveness, adverse effects, and risks and benefits of all contraceptives, with emphasis on the fact that the IUDs and the subdermal implant are the most effective methods of contraception.

They were then provided with the contraceptive of their choice and were allowed to discontinue or switch as many times as they wanted during the study period.

"About 75% of the women enrolled in our program chose a long-acting reversible contraceptive method at baseline," said Proehl.

During the study period, 30% of subjects experienced a gap in contraception. Users of long-acting contraceptives were significantly less likely to experience a gap than users of nonlong-acting contraceptives (18.5% vs 62.7%; P < .001).

In fact, users of nonlong-acting contraceptive were 7.17-times more likely to experience a gap, Proehl said.

Of the 567 unintended pregnancies during the study period, 480 were in women who experienced a gap — a rate of 20.3% in the gap group and 1.6% in the nongap group (P < .001).

The cumulative hazard of unintended pregnancy was 16.9 in the gap group, after adjustment for age, race, and baseline method of contraception.

"The take-home message is that gaps are associated with unintended pregnancy, and nonlong-acting contraceptive methods are strongly associated with gaps," said Dr. Peipert.

Because younger age was associated with gaps, young women are ideal candidates for long-acting contraceptive methods, he said, but not all of them want an IUD. "We're seeing that young teens sometimes prefer an implant over an IUD. One of those 2 methods should be right for teens. I'm not saying everyone needs an IUD, but I think everybody should first be presented with the option of a long-acting reversible contraceptive method."

The study is important because "it shows us one reason why women who use otherwise effective birth control methods become pregnant," Stephanie Teal, MD, from the University of Colorado Denver School of Medicine, told Medscape Medical News.

"We know that the pill, patch, ring, and medroxyprogesterone injection are very effective methods, yet women who use them get pregnant at a significantly higher rate than women who use passive birth control methods like IUDs and implants," she said. "The authors show that women using birth control methods that require daily, weekly, or monthly action are far more likely to have gaps in their contraceptive protection."

Cost is a big barrier to the uptake of long-acting methods, said Dr. Teal, who was not involved in the study. "Another barrier is whether women are able to access medical care.... Some providers require multiple appointments to get long-acting contraception, and some obstetrical providers don't provide long-acting contraceptive methods," she pointed out.

Dr. Peipert reports receiving research funding from Bayer and Merck. Ms. Proehl and Dr. Teal have disclosed no relevant financial relationships. Coinvestigator Tessa Madden, MD, MPH, reports receiving research funding from Merck and being on the advisory board for Bayer.

American Congress of Obstetricians and Gynecologists (ACOG) 61st Annual Clinical Meeting: Abstract SY05. Presented May 7, 2013.

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