Can you get pregnant on your period? It’s a common question women ask, whether they’re hoping to have a baby or trying to avoid pregnancy altogether. The answer can be tricky, given how confusing the timing of ovulation can be. That said, we reached out to experts to find out once and for all whether getting pregnant on your period—or directly before or after it—is even a possibility, and how to figure out when you’re least and most fertile.
Can You Get Pregnant on Your Period?
If you’re trying to conceive, timing when you have sex is a critical piece of the pregnancy puzzle. So can you get pregnant on your period? Answer: While extremely unlikely, it is technically possible, under rare circumstances.
To understand why, it’s important to know when ovulation and menstruation happen in your menstrual cycle. The average length of a cycle—from the first day of your period to the first day of your next period—is 28 days, but that varies greatly from person to person. In fact, cycles that last anywhere from 24 to 35 days are considered normal, says Jaime Knopman, MD, a fertility specialist in New York City and co-founder of Truly-MD.com.
As for the occurrence of ovulation—the midpoint in your cycle when a matured egg is released from your ovary—that again depends on the person, but most women ovulate between day 12 and 21 of their cycles. After the egg is released, it moves on to the fallopian tube, where it typically survives for 12 to 24 hours. There, it can meet up with any available sperm, which can usually live in a woman’s body for about three days and sometimes as long as five. What fluctuates less is when menstruation kicks in. Healthy women get their periods 12 to 14 days after ovulation if the egg isn’t fertilized, Knopman says, and bleed for four to five days on average.
So why is getting pregnant on your period so unlikely? It’s all a matter of simple math. Depending on when during your period you have sex, you’ll likely have at least seven days, if not more, before you ovulate. The sperm isn’t likely to survive that long, which is why, “a woman with a regular menstrual cycle will not get pregnant on her period,” says Fahimeh Sasan, DO, assistant professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai in New York City.
But here’s the snag: If a woman has very long periods (i.e., more than seven days long) and very short menstrual cycles, then she could get pregnant if that bleeding happens to take place during the time of her ovulation. “If you have a 21-day cycle, you’d likely ovulate around day seven. And if you’re still on your period by day seven, it may be possible to get pregnant,” says Megan Cheney, MD, MPH, medical director at the Women’s Institute at Banner-University Medical Center in Phoenix, AZ.
While the chances of getting pregnant on your period for most women with regular cycles are extremely low, this isn’t necessarily the case if you’re bleeding for other reasons. Some women have episodes of spotting between their periods, and even bleed (lightly) during ovulation. They may assume they’re on their period when, in fact, it’s their most fertile time of the month. That’s why it’s important for every woman to know her own unique menstrual patterns, Sasan says, and why, for women with irregular menstrual cycles, it’s especially important to use contraception if they’re not actively trying to conceive. (One useful clue: The blood you see during ovulation will either be light pink or brown, rather than the dark red of your period.)
When are the odds of getting pregnant the highest?
Bottom line: It’s very hard to get pregnant on your period—nearly impossible. So when can you get pregnant? Your best bet is leading up to and during ovulation. Since the egg is viable for only 12 to 24 hours after ovulation, it has to be fertilized by sperm before that time is up. Remember, sperm can live in your body for up to five days (though three days is more common), so it’s possible to have sex before you ovulate and still conceive a few days later. On average, a woman is fertile for the five days leading up to ovulation and up to 24 hours after. So if you wait 36 to 48 hours after ovulation to have sex, you’ll be beyond your window of fertility.
Keep in mind, it’s not unusual to take several tries before you become pregnant. Often times, both egg and sperm are available, but fertilization just doesn’t happen. According to one study on women with the mean age of 29, the odds of getting pregnant within the first month of properly timed sex was 38 percent, but that figure shot up to 68 percent after three months and 92 percent after a year.
Can You Get Pregnant Right After Your Period?
So it’s way harder to get pregnant on your period than when you’re not—but can you get pregnant right after your period? It depends on what you mean by “right after.” If you mean no more than one day after your period ends, then “in most cases, no,” Knopman says. The only exception? “If you have a very short cycle and long bleeding periods,” she says. In that case, if you bleed until day seven, have sex on day eight and ovulate on day nine or 10, it’s definitely possible to become pregnant.
For women with normal cycles, though, the chances of getting pregnant start to increase only as you get closer and closer to your window of fertility. Again, most women ovulate between day 12 and day 21 of their cycles—so if you have sex just two days after your period ends, say on day seven, you’re only five days away from ovulation. (So if you happen to have robust specimens of sperm swimming around—the ones that last as long as five days—there’s a chance you could get pregnant.)
Can You Get Pregnant Right Before Your Period?
The closer you are to your period when you have sex, the less likely you’ll get pregnant—since that puts you further away from the time of ovulation, and, as we mentioned, the egg lasts for only a day at most. So for women with a regular cycle, having unprotected sex the day before your period is extremely unlikely to result in a pregnancy—“almost zero chance,” Sasan says.