When Gwyneth Paltrow’s lifestyle site Goop devotes space to a feature about anal sex for hetero couples, it makes some waves. The Q&A with psychoanalyst Paul Joannides, author of The Guide to Getting It On!, delved into the history of anal and its rising popularity, as well as some how-to tips.

“First it was shocking, then it was having a cultural moment, now it’s practically standard in the modern bedroom repertoire—or so a quick scan of any media, from porn to HBO, will tell you,” the Goop editors wrote in the introduction. 

While research suggests anal isn't quite as prevalent as pop culture might suggest—a 2016 study found that just 12.2% of American women had done it within the last three months—there's no question curiosity about the backdoor position has grown. 

To find out more, we spoke with ob-gyn Lauren F. Streicher, MD, director of the Center for Sexual Medicine and Menopause at the Feinberg School of Medicine at Northwestern University. There are a few risks involved with anal that women need to know, she says.

“Let’s face it, the anus was not made for intercourse. It’s supposed to be a one-way passage,” Dr. Streicher points out. The vagina, on the other hand, “has a thick, elastic, accordion-like lining designed to stretch to accommodate a penis, or a baby.” 

Rectal tissue is thinner and doesn’t share the same elasticity, so there’s a greater chance it can tear, says Dr. Streicher, who is the author of Sex Rx. And tearing increases your odds of contracting a sexually transmitted infection. 

Rectal gonorrhea, anal chlamydia, and HIV are all real risks. According to the United States Centers for Disease Control and Prevention, "anal sex is the highest-risk sexual behavior for HIV infections." But anal sex is perhaps most likely to transmit the human papillomavirus (HPV). “Very few heterosexual men have HIV, but over half of men have HPV,” says Dr. Streicher. HPV can cause anal warts and anal cancer.

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What’s more, she points out, you’re probably not going to get screened for anal STIs at your doctor—unless he or she specifically asks if you’re having anal sex (unlikely) or you specifically request those tests.

Then there’s pain, bleeding, and fecal incontinence. “Poop in your pants is not a nice thing to talk about,” says Dr. Streicher. She points to new research from a team at Northwestern University that found that women who considered anal part of their regular bedroom behavior were more likely to say it changed the consistency of their stools, and report both urinary and fecal incontinence.

But if you're interested in trying anal sex, or giving it another whirl with your partner, what's the safest way? Use protection no matter what, says Dr. Streicher. “As a gynecologist, I tell people even if you are in a monogamous relationship, you should always use a condom for anal sex." And if you have vaginal sex after anal, have your partner put on a new condom to protect against the likelihood of a urinary tract infection.