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Providing birth control to women at no cost substantially reduced unplanned pregnancies and cut abortion rates by 62 percent to 78 percent over the national rate, a new study shows.

The research, by investigators at Washington University School of Medicine in St. Louis, appears online Oct. 4 in Obstetrics & Gynecology.

Among a range of birth control methods offered in the study, most women chose long-acting methods like intrauterine devices (IUDs) or implants, which have lower failure rates than commonly used birth control pills. In the United States, IUDs and implants have high up-front costs that sometimes aren't covered by health insurance, making these methods unaffordable for many women.

"The impact of providing no-cost birth control was far greater than we expected in terms of unintended pregnancies," says lead author Jeff Peipert, MD, the Robert J. Terry Professor of Obstetrics and Gynecology. "We think improving access to birth control, particularly IUDs and implants, coupled with education on the most effective methods has the potential to significantly decrease the number of unintended pregnancies and abortions in this country."

Unintended pregnancies are a major problem in the United States. Each year, about 50 percent of all U.S. pregnancies are unplanned, far higher than in other developed countries. About half of these pregnancies result from women not using contraception and half from incorrect or irregular use. The Contraceptive Choice Project enrolled 9,256 women and adolescents in the St. Louis area between 2007 and 2011. Participants were 14-45 years of age, at risk for unintended pregnancy, and willing to start a new contraceptive method.

Participants had their choice of birth control methods, ranging from long-acting forms like IUDs and implants to shorter-acting methods such as birth control pills, patches and rings.

The women were counseled about the different methods, including their effectiveness, risks and benefits. The extremely low failure rate (less than 1 percent) of IUDs and implants over that of shorter-acting forms (8 percent to 10 percent) was emphasized. In all, about 75 percent of women in the study chose IUDs or implants.

From 2008 to 2010, annual abortion rates among study participants ranged from 4.4 to 7.5 per 1,000 women. This is a substantial drop (62 percent to 78 percent) over the national rate of 19.6 abortions per 1,000 women in 2008, the latest year for which figures are available.

The lower abortion rates among CHOICE participants also is considerably less than the rates in St. Louis city and county, which ranged from 13.4 to 17 per 1,000 women, for the same years.

Among girls ages 15-19 who had access to free birth control provided in the study, the annual birth rate was 6.3 per 1,000, far below the U.S. rate of 34.3 per 1,000 for girls the same age.

While birth control pills are the most commonly used contraceptive in the United Sates, their effectiveness hinges on women remembering to take a pill every day and having easy access to refills.

In contrast, IUDs and implants are inserted by health-care providers and are effective for 5 to 10 years and 3 years, respectively. Despite their superior effectiveness over short-term methods, only a small percentage of U.S. women using contraception choose these methods. Many can't afford the cost of IUDs and implants, which can cost more than $800 and may not be covered by insurance.

"Unintended pregnancy remains a major health problem in the United States, with higher proportions among teenagers and women with less education and lower economic status," Peipert says. "The results of this study demonstrate that we can reduce the rate of unintended pregnancy and this is key to reducing abortions in this country."

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Washington University in St. Louis: http://www.wustl.edu