Anal sex is on the rise in terms of popularity, but many Americans seem to believe that this is a safe way to avoid sexually transmitted infections.

A recent study on heterosexual anal intercourse suggests that couples feel that it is a safe way to avoid HIV and other STIs. The study was presented at the 2016 American Congress of Obstetricians & Gynocologists (ACOG) annual meeting by a team of physicians from the University of Washington in Seatle. One of the authors of the study, Dr. Lyndsey Benson, talked with Plus about the study, its results, and what it means.

The study, named Survey of Motivations for Anal Sex among Heterosexuals (SMASH), surveyed 5,000 American men and women aged 15-50 years old. The study began after a previous study by Benson highlighted "many knowledge gaps" in regards to what Americans knew about anal sex, including information about condom use, frequency of engaging in anal versus penis into vagina (PIV) sexual practices, and knowledge of HIV risks. Benson, the lead researcher, explained that this study was particularly important, as the majority (84 perccent) of new HIV cases in women can be "attributed to heterosexual contact."

A full 36 percent of women surveyed by the study reported engaging in heterosexual anal intercourse (or HAI) atleast once. The researchers identified that this anal sex was being practiced primarily for self and partner pleasure or to simply satisfy curiosity.

However, penis in vagina sex is still the most popular form of sexual activity among heterosexuals.

The researchers also discovered that a disconcerting number of Americans were engaging in hetero anal sex as a way to avoid sexually transmitted infections including HIV. More than 70 percent of adults in the study incorrectly believe that vaginal intercourse is higher risk than receptive anal intercourse. Among those that had anal sex, 10 percent reported they had done so as a form of contraception at least once.

While pregnancy through anal sex is impossible, considered the riskiest activity for sexually transmitted infections because the anus does not naturally lubricate like the vagina, it's small and easily tears, and is host to both bacteria and the type of cells that are particularly appealing to STIs like gonorrhea, herpes, and chlamydia. Should there be a tear in the anal tissue (which occurs frequently with both anal sex and bowel movements), or an open pathway to the bloodstream such as through hemorrhoids, it is very possible to transmit HIV to a partner.

The information in Benson's study backs up a similar 2010 study conducted by the New York City Department of Health & Mental Hygene. That study suggested that there was in increase in anal sex among younger women, as well as women with multiple partners, and can be found here.

Benson's 2016 study has not yet been published.