Here’s what an ob-gyn wants you to know about unprotected sex and that time of the month. 

By Christina Oehler
June 17, 2019

Periods come with enough to stress out about: Cramps, cravings, and mood swings are just a few of the not-so-fun symptoms of your monthly menstruation. So you would think the one thing you could relax about is knowing you’re probably safe from getting pregnant, right? Wrong. Even though you and your S.O. may be totally cool with period sex, it doesn’t necessarily mean that it’s totally risk-free. 

So can you get pregnant on your period? The short answer is yes, it is possible—for two reasons.

“Every period is a bleed but not every bleed is a period,” Amanda Kallen, MD, assistant professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine tells Health. Kallen explains that a period, also known as a “withdrawal bleed,” is the bleeding you experience for two to seven days at the end of a menstrual cycle. This means that a woman is not pregnant, but is now starting her cycle over again, and will ovulate in a few weeks. 

RELATED: 10 Things That Mess With Your Period

However, explains Kallen, there are other reasons a woman will bleed from her vagina. Irregular cycles, polyps, and early pregnancy symptoms can all cause bleeding and can be mistaken for a period. 

“The risk here is that bleeding could be interpreted as a real period,” says Kallen. “A woman might think she is totally safe, but she’s not actually in that ‘safe’ part of her cycle.”

So what about when a woman is actually on her period? Kallen says that another possible way a woman can get pregnant on her period is if she has a longer menstrual cycle that lasts right up to when she begins ovulating.

RELATED: 12 Things Every Woman Should Know About Her Period

“If [a woman] has sex at the very end of her cycle and happens to ovulate on the earlier side, sperm could still be in her reproductive tract and she could conceive even though she had sex on her period because they can live for several days there,” says Kallen. 

Because sperm can live for up to five days inside a woman’s reproductive tract, it’s possible for one of those little swimmers to hang on until you ovulate, explains Kallen. Not to mention, many women’s cycles aren’t a perfect 28-days, so shorter periods and longer ovulations give sperm a better window to fertilize an egg. 

If you’re on an effective method of birth control and take it correctly, you have an even lower chance of getting pregnant on your period because most birth control pills prevent you from releasing an egg, Kallen explains. However, no birth control method is 100% effective, so while small, there is still a chance of getting pregnant while on your period and on birth control. 

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