HomeHealth TopicWomen's Health

Health Debunked: Can You Get Pregnant on Your Period?

Lindsay Boyers, CHNCSanjai Sinha, MD
Written by Lindsay Boyers, CHNC | Reviewed by Sanjai Sinha, MD
Published on June 27, 2022

Key takeaways:

  • Many people think that you can’t get pregnant on your period.

  • Because individual menstrual cycles vary, it is possible to get pregnant when you’re on your period.

  • If you don’t want to get pregnant, don’t rely on timing methods. Use the proper protection and/or birth control every time.

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There are many myths, misconceptions, and old wives’ tales about pregnancy. One of these myths is that you can’t get pregnant on your period. While conceiving during your period isn’t very common, it’s not unheard of. And for some people, especially older people and those with very regular cycles, the likelihood goes up a bit more. 

We dug into the science and chatted with Dr. Anne Hutchinson, M.D., an OB/GYN and reproductive endocrinologist at Shady Grove Fertility to bring you the facts.

How do you get pregnant?

Understanding the menstrual cycle is key to understanding how you get pregnant, according to Hutchinson, who broke it down like this:

  • The menstrual cycle starts with the first day of your period. This is the day that your brain realizes that you are not pregnant from the last egg that was released. Essentially, it’s the beginning of a new reproductive cycle. This is considered day 1.

  • Over the next two weeks, your brain communicates with your ovary to prepare an egg for ovulation. “Your body is then programmed to enter a 2-week holding pattern to give that egg a chance to meet sperm, make an embryo, and have that embryo implant and start to grow in the uterus,” Hutchinson explains.

  • If sperm doesn’t fertilize the egg, your next period will come 14 days later (this can vary based on your specific cycle), and the cycle will start over again. 

  • If sperm does fertilize the egg, you’ll become pregnant.

While the actual cycle is pretty predictable (assuming you don’t have any underlying hormonal issues), the individual timing — cycle length, ovulation day, and fertile window — varies between individuals, explains Hutchinson. 

Claim: You can’t get pregnant during your period

Because you’re not actively ovulating when you have your period, many people think that you can’t get pregnant during this time. Based on this thought, some people use a timing method, called the rhythm method or calendar method, to prevent pregnancy. 

The rhythm method involves tracking your menstrual cycle to predict when you’re ovulating. If you don’t want to get pregnant, you avoid intercourse during this time. If you do want to get pregnant, you plan intercourse around your predicted ovulation days.

Why do people think you can’t get pregnant on your period?

There’s no way to track down exactly where this idea came from, but it’s likely due to a misunderstanding about ovulation. Because ovulation typically occurs mid-cycle, or around days 14 to 16 on average, it seems logical that you can’t get pregnant on your period, which is day 1 of your cycle. But there are several reasons that this isn’t necessarily true and other important factors that can come into play.

What does the science say?

The science is settled on the fact that while it is a bit uncommon for it to happen, you can get pregnant on your period. 

In one study published in BMJ, researchers explained that only 30% of women have a predictable fertile window, which usually falls between days 10 to 17 of the menstrual cycle. That means that the other 70%, even those with regular cycles, have an unpredictable fertile window.

Because it’s unpredictable, it’s possible that part of the fertile window can overlap with your period. Older people and those with regular cycles are more likely to conceive earlier in the cycle, and according to one review, the probability of being fertile on day 4 of your cycle (which would be the fourth day of your period) is around 2%. This probability steadily increases until day 12, when it reaches 58%.

The other thing to consider is that while an egg can only be fertilized for 24 hours after ovulation, sperm can live in the cervix for up to 5 days. If you have unprotected intercourse during your period and your fertile window falls shortly after, the sperm may still be viable and result in pregnancy. This is more likely for those with shorter cycles. 

For example, Planned Parenthood notes that if your cycle is only 22 days long, it’s possible that sperm that enters the cervix on the last day of your period might still be in your body when you ovulate. If that happens, there’s a chance that you could become pregnant.

What do the experts say?

“The moral of the story is that while timing is very important when trying to get pregnant, there is enough natural variability in the menstrual cycle that timing should never be used as a way to prevent pregnancy,” says Hutchinson.

Timing can be tricky anyway, since not all bleeding is a period, Hutchinson explains. A “period” specifically refers to when the uterine lining sheds two weeks after ovulation, but there are plenty of other times when you may experience vaginal bleeding or spotting. 

“This can happen at any time during your cycle, and if you mistake this for a period, you might think that you can’t get pregnant even at times in your cycle when conception is most likely,” she says.

About 5% of women actually experience ovulation spotting — bleeding that occurs mid-cycle, when you’re ovulating. You may mistake this for the start of your period, but it’s actually a time when you’re most fertile.

So should you use your period as a birth control method?

Your period shouldn’t be used as a birth control method. Long story short: Nothing is impossible, cautions Hutchinson. “If you really don’t want to be pregnant, use protection every time,” she says. Or talk to your healthcare provider about birth control.

References

Dasharathy, S. S., et al. (2012). Menstrual bleeding patterns among regularly menstruating women. American Journal of Epidemiology.

Hutchinson, A. (2022). Shady Grove Fertility: Anne Hutchinson, M.D. [interview].

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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