Sixty percent of young adults between the ages of 18 and 29 may not truly understand how proper use of contraception can prevent pregnancy, according to a new study from the Guttmacher Institute, which reports abstinence-only sex education may be leaving young adults with a subpar understanding of sexual health.

After quizzing a nationally representative group of 1,800 unmarried women and men in that age group, the study, published in the journal Perspectives on Sexual and Reproductive Health, concluded that more than half of the respondents received low scores on contraceptive knowledge, with 60 percent reportedly underestimating the effectiveness of birth control pills.

The quiz asked respondents to choose true or false answers for basic statements such as all IUDs are banned from use in the United States or condoms have an expiration date. More than half of the men and a quarter of the women received either a D or F on the quiz.

Although a majority of the respondents -- 69 percent of women and almost half of the men -- agreed they were committed to avoiding pregnancy, they seemed to question whether contraceptive devices such as condoms or birth control pills were an effective way to achieve that goal. A considerable 40 percent of respondents said contraception doesn't matter because when it is your time to get pregnant, it will happen.

Those results may be particularly concerning since women between the ages of 18 and 29 have higher rates of unintended pregnancies than any other age group, the Guttmacher Institute reports.The study, which found that variables such as a fear of side effects (as a result of contraceptives) and mistrust of government's role in promoting contraception was associated with risky birth control practices, concluded that programs to increase young adults' knowledge about contraceptive methods and use are urgently needed.

The new report is far from the first study to point out the educational gap that is often a consequence of abstinence-only policies. While the U.S. Centers for Disease Control and Prevention recently reported teen pregnancies in 2010 dropped to the lowest rate since 1940, it found that states with abstinence-only programs continue to experience higher rates of teen pregnancies.

Thirty-seven states currently require sex education that includes a discussion of abstinence, while 26 of those require that abstinence be stressed as the best way to prevent unwanted pregnancies and sexually transmitted diseases. Conservative lawmakers have continued to push for abstinence-only policies, despite the fact that they have proven to be ineffective time and time again. In 2007, a federal report submitted to the Department of Health and Human Services found those programs have had no impact on rates of sexual abstinence and students who received abstinence-only sexual education had considerably less knowledge about the risks of unprotected sex.

The report is particularly timely as it was released on the heels of the Obama administration's recent decision to support an abstinence-only curriculum as part of the Department of Health and Human Services pregnancy prevention programs. In April, Heritage Keepers Abstinence Education was quietly added to an Office of Adolescent Health list of approved groups eligible for government funds. A curriculum for the program stresses the benefits of abstaining from sexual activity until marriage and does not include any information about condoms or birth control pills.