Can you get pregnant if you have your period

Think you don't need to use protection if you have sex on your period? As it turns out, that's not entirely true. "It's technically possible to get pregnant while on your period, but it's rare for this to happen," says Barbara Stegmann, M.D., a triple board-certified OB-GYN and women's health clinical lead at Organon. Keep reading to learn why it's possible to conceive by having sex during menstruation.

Understanding Your Menstrual Cycle

For starters, it helps understand your menstrual cycle. "A period is defined as the blood loss that happens at the end of an ovulatory cycle, as the result of an egg not being fertilized by a sperm," explains Michele Hakakha, M.D., a board-certified obstetrician and gynecologist based in Los Angeles and co-author of Expecting 411: Clear Answers and Smart Advice for Your Pregnancy.

"Every month, a woman releases an egg on approximately day 14 of her cycle," says Dr. Hakakha—though ovulation date varies for everyone, and it's also possible to have irregular cycles. "Prior to the release of the egg, the hormones in a woman's body increase to prepare (and thicken) the lining of the uterus in case the egg is fertilized and a pregnancy occurs. If there is no fertilization, the lining of the uterus is sloughed off about 14 days later. This is called your period." Most people have periods that last from two days to eight days and take place every 26 to 34 days.

Ovulation typically occurs midway through the cycle, and it's the most fertile time in your menstrual cycle—meaning when you're most likely to conceive. Because sperm can survive for several days in the reproductive tract, a woman can get pregnant by having sex during ovulation or the days leading up to it.

Can You Get Pregnant During Your Period?

Most people have menstrual cycles that last 26 to 34 days, and if someone with this cycle has an average two- to eight-day period, they will probably not get pregnant during their period. An egg that is released during ovulation but remains unfertilized "comes out with all of the menstrual blood," Dr. Hakakha explains.

That said, the chance of pregnancy on your period increases if you have an irregular cycle. "A woman with a shorter menstrual cycle (24 days, for example), could have seven days of bleeding, have intercourse on her final day of bleeding, and ovulate three days later," Dr. Hakakha says. "Since sperm live for three to five days, she could definitely get pregnant" if it fertilizes a released egg, which has a lifespan of about 24 hours.

In addition, some women experience breakthrough spotting or bleeding between periods. This can occur during ovulation and be mistaken for a period, making it difficult to establish the exact place in the menstrual cycle. Having sex during ovulation increases your chances of getting pregnant.

The Bottom Line

"Unprotected intercourse can result in pregnancy if the sperm and egg can get together and you are off in your timing estimates," says Lauren Sundheimer, M.D., MS, FACOG, an OB-GYN practicing in Orange County, California. "If you are able to track your fertile window, then having intercourse outside of when you are considered fertile or when you are nearing ovulation might be safe, but there is never a guarantee that you will not get pregnant."

Your period came, so does that mean you can be a little more lax about birth control? After all, you can’t get pregnant while Aunt Flo is around, right?

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Unfortunately, that’s not true. You can get pregnant during your period.

• If you didn’t ovulate in the middle of your cycle.

• If your periods aren’t regular — so you don’t ovulate regularly.

• If you have a short menstrual cycle.

It’s not quite that simple, says Ob/Gyn Amy Stephens, MD. She clears up the confusion about fertility and your monthly cycle.

Fertility windows

The most fertile time of your cycle, when you are most likely to get pregnant, is when you ovulate, or release an egg, Dr. Stephens explains. That typically happens midway between periods.

So if you have a regular 28-day cycle, Day 1 would be the first day of your period, and you would ovulate around Day 14. “You have the highest chance of getting pregnant during the few days before and after that day,” she says.

But that’s a general guideline and not a rule. “You can definitely get pregnant outside that window,” Dr. Stephens says.

Ovulation timing

If you have unprotected sex during or right after your period, there is a lower chance of getting pregnant. “But the chances are not zero,” Dr. Stephens stresses.

That’s especially true for women with irregular periods, whose ovulation date is harder to predict. Even women who normally have periods like clockwork can experience an unpredictable cycle as the result of things like stress, hormonal changes, and losing or gaining weight.

Having a shorter-than-average cycle also increases your risk of conceiving during period sex. That’s because sperm can live inside you for up to 5 days. They could still be hanging around, looking for love, if you release an egg 4 or 5 days after your period ends.

How not to get pregnant

If you want to get pregnant, plan to get frisky halfway between periods for the best chances. But if you’re trying to avoid pregnancy, don’t use your period as a guide. Instead, choose a reliable form of birth control.

“That’s the best way to prevent pregnancy,” Dr. Stephens says. 

Yeah, you probably already knew that. But now you know the whole story.

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