Dr. Jeffrey F. Peipert, the Robert J. Terry Professor of Obstetrics and Gynecology at Washington University School of Medicine in St. Louis, and colleagues analyzed data of the Contraceptive CHOICE Project, a study of 9,256 adolescents and women at risk for unintended pregnancy.
Participants were provided reversible contraception of their choice at no cost and were followed-up with telephone interviews at six and 12 months.
"We examined the number of male sexual partners and sexual intercourse frequency reported during the previous 30 days at baseline compared with six-month and 12-month time points," the researchers wrote in the study.
All of the women, ages 15 to 45, were either sexually active with men or planning to become active when the study began -- 5 percent were virgins.
The study, published in Obstetrics & Gynecology, found 3.3 percent reported more than one partner the previous month, down from 5.2 percent at the beginning of the study, while 16 percent increased the number of partners -- most often from zero to one.
The study also found the median number of times women had vaginal intercourse rose from four times a month to six times a month.
However, despite the increase in the number of times the women has sexual intercourse from four times a month to six after receiving the free contraception, they did not result in greater sexually transmitted infection incidence at the 12-month point of the study.
About half of the women who said they were virgins at the beginning of the study were still virgins at the end of the study.