Period sex is great for so many people. At the very least, it sure as heck beats the alternative of forgoing sex one week out of every month (adds up quick). But it does beg an obvious question with a not-so-obvious answer: Is period sex a get-out-of-jail-free card for avoiding an unintended pregnancy?
Dr. Alyssa Dweck, a gynecologist in New York, said it's complicated. By definition, a period is a shedding of the uterine lining in the absence of a fertilized egg (in layman's terms, a pregnancy). But not everyone has regular periods, and a lot of people experience breakthrough bleeding or spotting around the time of an expected period, and that bleeding isn't actually a period.
"Lots of women with certain hormonal balances will have this happen," she said, and added that most of the patients she sees who get pregnant even though they thought they were on their period have a condition called polycystic ovary syndrome, or PCOS, that causes irregular menstrual cycles.
What you need to be sure of is that you already ovulated, and the bleeding you're experiencing is a true period. If both of those things are true, it's highly unlikely you'll get pregnant. But! A fun fact about sperm that once you know you can never un-know is that they are capable of living in your body for up to five days. The average menstrual cycle is 28 days long, but anything between 24 and 35 days is considered normal, Dweck said. Most people ovulate between day 11 and day 21 of their menstrual cycle (with day one marked as the first day of a period) and the egg hangs out in the fallopian tube for 12-24 hours, waiting to be fertilized.
All of this timing is important. While the average period is about four to seven days long, let's say your period lasts longer, and you have a short menstrual cycle (less than 24 days). If you have sex at the very end of your period and then ovulate immediately after or a few days later, because of the short cycle, it may be possible to get pregnant – since that sperm could still be alive.
Again, this is highly unlikely. But it is enough of a reason to carefully track your menstrual cycles, periods, and ovulation. And it literally never hurts to be too careful when it comes to taking precautions to avoid unintended pregnancy. If you use a condom or birth control the entire rest of the month, might as well continue to do so on your period.
This post was originally published in 2004 and has been updated.
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