February 28, 2013 — "Misunderstanding the Risk of Conception from Unprotected and Protected Sex," Biggs/Greene Foster, Women's Health Issues, Jan. 23, 2013.
"There are many reasons why couples not wanting to get pregnant may not use contraception," but "[o]ne of the top reasons reported by women ... is the belief that they cannot become pregnant," according to Antonia Biggs and Diana Green Foster of the University of California-San Francisco's Bixby Center for Global Reproductive Health. The researchers completed a study to expand "understanding of the factors associated with women's knowledge about the risks of conception from engaging in unprotected sex and when having sex while using condoms," oral contraceptives (OCs) and intrauterine devices (IUDs).
They noted that women also might forego contraception because of barriers to access, challenges negotiating contraception use, a lack of understanding, negative attitudes about contraception or perceived benefits of having unprotected sex. "[M]any women not desiring pregnancy held positive beliefs regarding unprotected sex, such as the feeling that it feels better and is more natural, is safe certain times of the month, and enhances one's relationship," the researchers stated.
"Understanding women's perceptions of their risk of conception from either unprotected sex or from sex while using birth control is crucial to understanding why couples risk an unintended pregnancy," they wrote.
The researchers analyzed a subset of data from a larger study involving women who sought services at 13 U.S. family planning clinics between January 2011 and May 2011. Eligible women were ages 15 or older, spoke English or Spanish, and had never had an abortion.
The respondents answered various questions about "contraceptive attitudes," including the chances of becoming pregnant during unprotected sex and with various contraceptive methods, how often they had sex and used contraception, and whether they were considering obtaining contraception that day.
Among the 1,543 women included in the study, 8% accurately assessed the chances of pregnancy from one act of unprotected intercourse (UI) and 92% "greatly overestimated" the risk of pregnancy from one act of UI. About 24% "greatly underestimated" their risk of pregnancy after one year of UI.
When asked about different methods of contraception, 16% of respondents were able to accurately assess that the risk of pregnancy from one year of condom use is between 10% and 20%. Additionally, 10% thought the risk is between 20% and 30%, 30% thought it is lower than 10%, and 44% thought it is greater than 30%.
Forty-eight percent accurately gauged the risk of pregnancy from one year of OC use, compared with 39% who "greatly overestimated" pregnancy chances from OC use. About 56% accurately assessed the chances of pregnancy from one year of IUD use, while the remaining 44% overestimated the risk of conception from IUD use.
"[M]ost women believe that the chance of pregnancy from one act of UI is far greater than it actually is," Biggs and Greene Foster wrote.
They noted that some of the estimates of the risk of conception from one act of UI "were so high that they were very similar to the risk women reported for 1 year of UI, suggesting that there is a lack of understanding with regard to the high cumulative risk from repeating a low-risk activity."
They found that nearly half of the women in the study said they engaged in UI because they do not think they will become pregnant, which is consistent with "other studies that have found that women who underestimate their fertility potential are less likely to use contraception."
Women also "doubted the effectiveness of condoms, OCs, and [IUDs]," the study found. Women in demographic groups with the highest rates of unintended pregnancy -- African-American, Latina, poor, and less educated women -- were the most likely to underestimate the effectiveness of contraception, according to the study.
Noting that the study was restricted to women who had never obtained an abortion, they added, "It is likely that women who have had an abortion have very different perceptions of pregnancy risk than women who have not."
"Our findings suggest a need to strengthen women's knowledge about method effectiveness, particularly among women of lower educational and income levels and ethnic minority women," Biggs and Greene Foster wrote, adding, "Improved understanding of the risks women take when they engage in unprotected sex and of the protective effects of using higher efficacy birth control methods has the potential to ensure more consistent contraceptive use."
Debra Ness, publisher & president, National Partnership
Andrea Friedman, associate editor & director of reproductive health programs, National Partnership
Marya Torrez, associate editor & senior reproductive health policy counsel, National Partnership
Melissa Safford, associate editor & policy advocate for reproductive health, National Partnership
Perry Sacks, assistant editor & health program associate, National Partnership
Cindy Romero, assistant editor & communications assistant, National Partnership
Justyn Ware, editor
Amanda Wolfe, editor-in-chief
Heather Drost, Hanna Jaquith, Marcelle Maginnis, Ashley Marchand and Michelle Stuckey, staff writers
Tucker Ball, director of new media, National Partnership