Can You Get Pregnant on Your Period?

Can you get pregnant on your period? As it turns out, you can, but it is not common. "It's technically possible to get pregnant while on your period, but it's rare for this to happen," says Barbara Stegmann, MD, a triple board-certified OB-GYN and women's health clinical lead at Organon.

Keep reading to learn how it's possible to conceive by having unprotected penis-in-vagina (PIV) sex during menstruation.

How Conception Works

To learn how it's possible to get pregnant on your period, it helps to understand the menstrual cycle. Each cycle, an egg is released from the ovaries, known as ovulation. Ovulation typically occurs about two weeks (or about 12 to 14 days, though this can vary) before a person gets their period.

After the egg is released, it travels down the fallopian tube, where it lives for approximately 12 to 24 hours while it awaits fertilization with sperm. Sperm can survive for several days in the reproductive tract, so a person can get pregnant by having sex during ovulation or the days leading up to it, explains Michele Hakakha, MD, a board-certified obstetrician and gynecologist based in Los Angeles and co-author of Expecting 411: Clear Answers and Smart Advice for Your Pregnancy.

"Prior to the release of the egg, the hormones in a [the] body increase to prepare (and thicken) the lining of the uterus in case the egg is fertilized and a pregnancy occurs," says Dr. Hakakha. "If there's no fertilization, the lining of the uterus is sloughed off about 14 days later. This is called your period."

In other words, a period is the blood loss that happens at the end of an ovulatory cycle as the result of an egg not being fertilized by sperm.

Is It Possible To Get Pregnant on Your Period?

Yes, while unlikely for most menstruating people, it's possible to get pregnant while you are on your period. Here's how: You can only get pregnant by having sex during ovulation or the days leading up to it (you can calculate this fertile window using an ovulation calculator). But if you have unprotected penis-in-vagina sex near the very end of your period and then go on to ovulate very soon after your period ends, you could catch that "fertile window."

Studies show that most people have menstrual cycles that last 26 to 34 days with periods that last from two days to eight days. Since ovulation occurs about two weeks before menstruation, most people will ovulate well after their period ends (and beyond the window that sperm can survive in the female reproductive tract after ejaculation).

That said, the chance of getting pregnant on your period increases if you have a short cycle and a longer period. A person with a shorter menstrual cycle (24 days, for example) could have seven days of bleeding, have intercourse on their final day of bleeding, and ovulate three days later, says Dr. Hakakha. Since sperm can live for three to five days, a person could definitely get pregnant if that sperm fertilizes the released egg, which has a lifespan of about 24 hours.

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

The Chances of Getting Pregnant on Your Period

You're unlikely to conceive by having sex on your period, but it can happen. Consider the results of a 2013 study, which analyzed conception probabilities from 5,830 people. The study found that the chance of conception rises seven days after your last menstrual period, and it peaks at 15 days. That said, researchers found a 2% probability of "being within the fertile window" at day four—and many people are still on their period during that time.

The following factors increase the odds of getting pregnant on your period:

• Irregular periods
• Short menstrual cycles
• Spotting or mid-cycle bleeding that's mistaken for a period
• Period bleeding that lasts a long time, carrying over into your fertile window

Can You Get Pregnant Right After Your Period?

After menstruation, you're moving closer to the fertile window each day. Just as it's possible to get pregnant while you're on your period, it's possible to get pregnant right after your period if you ovulate around that time.

During a typical cycle (26 to 34 days), ovulation will occur around day 12 at the lower end or day 20 at the high end. The fertile window, or the time during which it is possible to conceive, will begin three to five days before ovulation.

For someone with a 26-day cycle, that means that they could potentially get pregnant as early as day seven. Depending on the length of their period, this could be right after their period ends. The shorter the cycle, the more likely it is that the person will enter their fertile window shortly after their period.

Can You Get Pregnant Right Before Your Period?

There's a low chance of conception by having sex right before your period. After an egg is released during ovulation—which usually happens about two weeks before menstruation—it only survives for 12 to 24 hours in the reproductive tract. If it's not fertilized during this time, it can't form a pregnancy. You'll need to wait until your next fertile window to conceive.

Of course, there's no guarantee when having unprotected sex, so you'll still want to be diligent about using birth control if you're not trying to conceive. This is especially true for people with irregular cycles.