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The participants were less likely to have sex with more than one man after the program began. And though they did have sex a bit more often, they were no more likely to be diagnosed with sexually transmitted diseases, according to results published online Thursday in Obstetrics & Gynecology.
The same study, involving 9,256 girls and women in the St. Louis area, previously showed the free birth control program dramatically reduced abortions and unintended pregnancies.
The latest findings should dispel "the idea that the only thing standing between women and promiscuity is a fear of pregnancy," says project director Gina Secura, a researcher at Washington University.
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The study addresses related concerns, from social conservatives who have speculated that widespread free birth control would encourage sexual promiscuity. The paper specifically mentions such criticisms from the non-profit Family Research Council.
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For the new analysis, researchers looked at data on 7,751 participants ages 14 to 45 who completed follow-up surveys. All were either sexually active with men or planning to become active when the study began. Among those without partners at the start, just 5% were virgins.
Among the results 12 months after participants got free birth control medications or devices:
• 3.3% reported more than one partner the previous month, down from 5.2% at the beginning of the study.
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• The median number of times women had vaginal intercourse in a month was six, up from four.
• Rates of gonorrhea and chlamydia were the same among women who increased their sexual frequency and those who did not.
• 46% who were virgins at the beginning of the study were still virgins, despite their earlier intentions to start having sex.
"It's not as if getting birth control opened the floodgates" on sexual activity, Secura says.
But Grossu says the study does not show whether results differed between new and previous contraceptive users and does not include any comparisons with non-participants, a so-called control group. She also notes that the women were surveyed by phone, rather than in the privacy of a clinic, possibly leading to less truthful responses — a limitation the researchers also note in their paper.
The researchers also note that about 16% of project participants did not take the follow-up surveys, and that it's possible those women were a higher-risk group than those who did take the surveys.