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Can you get pregnant on your period?

Can you get pregnant on your period?

Catherine Poslusny | July 1, 2020 | Women's Health

In the world of female reproductive health, a consistent lack of research and abundance of misinformation can make it difficult to tell whether the things we’ve learned about periods and fertility are based in science or old wives’ tales. Most of us have heard, at some point or another, that it’s impossible to get pregnant while you’re on your period, but is that actually true? 

Whether you’re trying to conceive or trying to avoid getting pregnant, knowing when you’re fertile could help you make important decisions about when (and how) you have sex. In this post, we’ll take a look at ovulation, menstruation, and whether you can get pregnant while you’re on your period.

Can you get pregnant while you’re on your period?

The short answer is, for many people, probably not; however, figuring out whether you’re one of those people is a little more complicated. It all depends on when you ovulate during your menstrual cycle and how close ovulation is to the days you’re on your period. 

Menstruation and ovulation: a crash course

Your period signals the beginning of your cycle: day 1. During menstruation, which typically lasts between 4 and 8 days, your body breaks down and sheds your uterine lining, which thickened in preparation for a fertilized egg (1). 

While it may seem like your uterus is closed for business during your period, it’s actually getting ready for your next ovulation. In the beginning of your cycle, follicles (pockets of fluid) start maturing eggs in your ovaries. The maturation process takes an average of 2 weeks, but can take anywhere from 8 to 21 days (8). 

When the egg is released from your ovary, it can live for 12 to 24 hours and must be fertilized within this time for you to get pregnant (1). 

Read about the Phases of the Menstrual Cycle for all the details on your amazing cycle.

When is it possible to get pregnant during your period?

As we discussed, your uterine lining is shedding when you’re on your period. In other words, there’s no egg to fertilize, which means you can’t conceive during menstruation. But you can get pregnant from unprotected sex during your period (8). 

That’s because sperm can stay alive in the female reproductive tract for up to 5 days after you have unprotected sex. If you add the sperm lifespan and egg lifespan together, you’ll see that having sex as many as 5 days before or 1 day after ovulation could result in a pregnancy. This 6-day period is called your fertile window, and it’s the only time that you’re able to get pregnant during each menstrual cycle (2). If any part of your fertile window overlaps with your period, then having unprotected sex during your period may lead to a pregnancy. 

A few factors could make your period more likely to overlap with your fertile window. For example, if your menstrual cycle is less than 28 days, you may ovulate sooner than those with longer cycles. If you have irregular cycles, that may also increase the chances of ovulation near the end of your period (3). 

Your chances of conceiving from sex during menstruation also depend on which day of your period you have sex. Each day that passes brings you closer to the day of ovulation. Consider this: if your period lasts 7 days and you have unprotected sex on day 7, then you ovulate on day 12 (or sooner), that unprotected sex on the last day of your period could result in a pregnancy (4). 

A note on non-period bleeding

Not all vaginal bleeding is menstruation. For example, changes in hormone levels may cause spotting around the time of ovulation (during which you’d have a significantly higher chance of getting pregnant than during your period) (5). The presence of vaginal bleeding, whether it’s from your period or another cause, shouldn’t be used as an indicator that you’re not fertile.

Can you get pregnant right before or after your period?

The days following ovulation, after your fertile window has closed, are when you’re least fertile. This means that unprotected sex in the days before your period is not likely to lead to pregnancy (though it’s impossible to be sure without confirming when you ovulated). The opposite is true of the days right after your period, during which you’re closer to ovulation than you were during your period (4). 

How can you know when you ovulate?

Though there are guidelines or averages for the different days of the menstrual cycle, they don’t account for the vast variances in individual cycles. As many as 70% of women ovulate before day 10 or after day 17 of their cycle, pushing their fertile windows earlier or later. Plus, ovulation doesn’t always occur on the same day every cycle, even in people with predictably regular cycles (6). 

There is no one-size-fits-all formula to figure out when you ovulate, however, your body goes through a series of changes during each menstrual cycle that can indicate ovulation. Learning these signs helps you make informed decisions about sexual activity, depending on your goal. This is called using a fertility awareness-based method (FABM) of natural family planning (7).

(Want to learn more? We break down the most popular FABMs here). 

While it’s not likely to get pregnant from having sex while on your period, it’s definitely not impossible. Whether you’re trying to get pregnant or avoid a pregnancy, the presence of your period isn’t the most reliable indicator of your fertility. Figuring out when you ovulate—not when you menstruate—is the best way to determine whether you’re having unprotected sex during your fertile window.