IUDs More Effective Than The Pill At Preventing Pregnancy: Study
May 24, 2012

IUDs More Effective Than The Pill At Preventing Pregnancy: Study

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In a new study of birth control methods and unintended pregnancies, researchers have found that the pill is the most popular method of contraception used in the US, however it may not be the most effective.

The study found that more US women got pregnant while using short-acting methods such as pills, patches and vaginal rings -- and that the highest rate of unintended pregnancies was seen in women under 21 years of age.

Researchers at Washington University School of Medicine in St. Louis found that less popular, longer-term options are much more effective.

An implant placed under the skin of the upper arm to secrete hormones steadily over three years, and an intrauterine device (IUD) placed in the womb for up to ten years, were both found to be more effective at preventing pregnancy than the other more popular methods used.

In the study, published Wednesday in the New England Journal of Medicine, researchers asked 7,500 women and teens in the St. Louis area to pick from a variety of contraception methods at no cost.

Participants were interviewed by telephone at three and six months and every six months thereafter for the remainder of the study. During each interview, participants were asked about missed periods and possible pregnancy. Any participant who thought that might be pregnant was asked to provide a pregnancy test. Those who were pregnant were asked if it was intended and what contraceptive method (if any) they were using at time of conception.

During the three-year study period, 334 of those participants who completed all follow-up interviews had an unintended pregnancy. Of these, 156 pregnancies were due to contraceptive failure: 133 of women using pills, the patch or ring, and 21 of women using IUDs and implants.

“We found 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,” research team leader Dr. Brooke Winner told Reuters.

The team found that birth control pills and other short-term contraception methods were especially unreliable among younger women. For those under 21 who used the pill, the patch or the ring, the risk of unintended pregnancy was nearly twice as high as the risk among older women.

“This study is the best evidence we have that long-acting reversible methods are far superior to the birth control pill, patch and ring,” said study coauthor Jeffrey Peipert, MD, the Robert J. Terry Professor of Obstetrics and Gynecology. “IUDs and implants are more effective because women can forget about them after clinicians put the devices in place.”

Unintended pregnancy is a significant problem in the US with as many as 3 million unplanned pregnancies per year -- about 50 percent of all pregnancies. And the rate of unintended pregnancy in the US is much higher than in any other developed nation. Previous studies have shown that nearly half of all unintended pregnancies in the US are the result of contraceptive failure.

The most reliable methods -- hormonal implants and IUDs -- have steep up-front costs, however, and many women cannot afford them.

“We know that IUDs and implants have very low failure rates –less than 1 percent,” said Winner. “But although IUDs are very effective and have been proven safe in women and adolescents, they only are chosen by 5.5 percent of women in the United States who use contraception.”

Winner said the study was significant because “it showed that when IUDs and implants are provided at no cost, about 75 percent of women chose these methods for birth control.”

Women who chose an IUD or implant tended to be older, have public health insurance and have more children than those who chose the contraceptive methods, who were more likely to have private health insurance and not have had any children previously.

The study results support a shift in how patients should be counseled, which could greatly affect unintended pregnancy rates, noted Peipert.

“If there were a drug for cancer, heart disease or diabetes that was 20 times more effective, we would recommend it first,” he said. “Unintended pregnancies can have negative effects on women's health and education and the health of newborns.”