New research shows that providing women with free contraception does not increase the likelihood that they will have sex with multiple partners, as critics of the practice have suggested.

The study, by researchers at Washington University School of Medicine in St. Louis, appears online March 6 in Obstetrics & Gynecology.

“The notion that women will have sex with more partners if you give them free birth control didn’t pan out in this study,” said Jeffrey Peipert, MD, PhD, the study’s senior author and the Robert J. Terry Professor of Obstetrics and Gynecology. “Providing no-cost contraception did not result in riskier sexual behavior.”

The researchers analyzed data from the Contraceptive CHOICE Project, a study of 9,256 women in St. Louis who were at high risk for unintended pregnancy. The women were told of the superior effectiveness of long-term contraceptives such as intrauterine devices and implants over birth control pills, patches and rings and allowed to choose among the contraceptive methods, which were provided at no cost.

Earlier studies of women in the CHOICE project showed that providing women with no-cost birth control substantially reduces unintended pregnancies and abortions.

In the new analysis, the researchers looked at whether providing no-cost contraception to CHOICE participants increased their number of sexual partners and frequency of intercourse in the year after they received no-cost contraception. Both are measures of sexual risk behaviors linked to pregnancy and sexually transmitted infections.

“Having multiple partners is a known risk behavior,” said Gina Secura, PhD, the study’s first author and project director of the CHOICE project. “If sexual behavior were going to change after women received free contraception, you would expect to see that change soon after they got the birth control.”

Women in the current study ranged in age from 14 to 45. Thirty-two percent had a high school education or less, 35 percent received public assistance and 39 percent had trouble paying for basic expenses. Forty-nine percent had never had a child, and 62 percent had a prior unintended pregnancy.

The women were surveyed about their sexual behaviors six months and 12 months after receiving free birth control. Each time, they were asked about their frequency of sexual intercourse and the number of partners in the previous 30 days. About 7,750 women (85 percent) completed both surveys and were included in the current analysis.

The percentage of participants who reported multiple partners declined throughout the study. At the beginning of the study, 5.2 percent reported more than one male sexual partner compared with 3.5 percent at six months and 3.3 percent at 12 months. Most of the women surveyed (70 percent) reported no change in the number of sexual partners at six months and at 12 months, whereas 13 to 14 percent reported a decrease and 16 percent reported an increase.

Among those participants who reported an increase in the number of partners, more than 80 percent had an increase from no partner to one partner.

In all participants, frequency of intercourse increased from four episodes at the beginning of the study to six episodes at the six-month and 12-month marks. However, more frequent intercourse did not increase the incidence of sexually transmitted infections at 12 months.

“Increasing access to no-cost contraceptives doesn’t translate into riskier sexual behavior,” Peipert said. “It’s not the contraception that drives their sexual behavior.”

This research was funded in part by the National Institutes of Health (NIH).

Secura GM, Adams T, Buckel CM, Qiuhong Z, Peipert JF. Change in sexual behavior with provision of no-cost contraception. Obstetrics & Gynecology. March 6, 2014.

Washington University School of Medicine’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s hospitals. The School of Medicine is one of the leading medical research, teaching and patient-care institutions in the nation, currently ranked sixth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.