How likely is it to get pregnant before your period

Whether you are trying to conceive or want to avoid pregnancy without birth control, the timing of intercourse is important. You're most likely to conceive mid-cycle during ovulation. It's much less likely that you could get pregnant from having sex immediately before or during your period. But because many people have irregular menstrual cycles, perfect timing—to get pregnant or ensure you don't—can be tricky.

One thing is for sure: Conception can only occur during the time you're ovulating, about midway through your cycle. Ovulation lasts 12 to 48 hours, and eggs released from your ovaries during that time live for about a day. Sperm, meanwhile, can typically only survive in your reproductive tract for around 72 hours. That means that having sex from about four days before you ovulate to about one day after could result in pregnancy.

That six-day period during each menstrual cycle is known as your fertile window. Unfortunately, the timing of that fertile window can differ from person to person and even month to month. For that reason, while there are times of the month that make you more likely to conceive, there is a small chance you can get pregnant closer to your period than you think. That said, it's very unlikely to be pregnant if your period starts after sex.

Sex Immediately Before Your Period

By and large, your likelihood of conceiving right before your period is very low. Once you're a day or two before your period, the chances are that you've already ovulated and the released eggs are no longer viable, as they only live for about 24 hours.

Ovulation usually occurs several days to a week or more before menstruation begins: about midway between the first day of your last menstrual period (day 1 LMP) and the start of your next one.

A "typical" cycle is 28 days long, but many people have slightly shorter or longer cycles. In one study of 32,595 people, people with self-reported regular periods had menstrual cycles ranging from 23 to 35 days long. The most common day to ovulate is day 15 LMP.

If you are trying to be mindful of your cycles as a natural form of birth control, be aware there's a slight chance of pregnancy if you ovulate later in the cycle or simply miscalculate the dates of your next period. In one large study, even people who reported having regular menstrual cycles had a 6% chance of being in their fertile window on the day they expected their next period to begin.

The bottom line is that if you are trying to conceive, right before you expect your period would not be the best time to start. You can still enjoy sex, of course, but you are much more likely to get pregnant if you try again after your period.

A typical cycle is 28 days long, though some people might experience shorter or longer cycles—and it might not be the same every time. You're most likely to get pregnant during ovulation, which typically occurs about halfway through your cycle.

Sex During Your Period

The chances are pretty good that you will not get pregnant if you have sex during your period. Menstruation is the signal that the ovum was not fertilized or implanted, leading to a drop in hormone levels and the shedding of the uterine lining. Even if a sperm made it to an egg, which is very unlikely, the uterine lining would not be ready for implantation. So, during this stage in your cycle, your risk of pregnancy remains negligible.

However, the odds of conception during your period aren’t zero. If you have a very short cycle, ovulation may occur soon after your period. Given that sperm can live inside you for up to three days, having sex at the end of your period may lead to fertilization in the days following it. One study charting the most common conception days in the menstrual cycle shows that odds start to rise on day 7 LMP—just a week past your first day of bleeding.

It's also important to note that what you may think is a period might not be. An estimated 2.8% of people with periods have spotting around ovulation, which is actually when you are most fertile. In other cases, spotting may be implantation bleeding, a very early sign of pregnancy. Unlike a regular period, spotting in these circumstances is typically lighter in color and flow.

Sex Right After Your Period

While you may assume that your odds of getting pregnant are slim in the first few days following your period, you are actually moving into a new fertility window. Researchers have shown that a person's chances of conception jump starting a week after the start of their last period and rise steadily after that, peaking around day 15 LMP.

Your odds of getting pregnant in the days just following your period rise when you have a shorter length between periods because that usually means you ovulate soon after your period ends. Research has shown that people with a 23-day menstrual cycle, for instance, have a 9% chance of ovulating on day 10 LMP. That means they are fertile—able to get pregnant—between six and 11 days after the start of their last period.

Remember, even when you are in your suspected fertile window, that does not mean you will necessarily get pregnant from sex. Structural problems with your uterus or fallopian tubes or issues with either your eggs or your partner's sperm can prevent conception and fertilization. If you are timing sex to get pregnant and having trouble after several months, consider talking to a fertility doctor about tests you can take to better understand how to maximize your chances of conception.

A Word From Verywell

It's very unlikely to be pregnant if you had sex and then got your period. Your chance of conceiving inches upward in the days following the end of your period. Doctors typically recommend that couples who are trying to have a baby have sex between days 7 and 20 of their menstrual cycle (counting from the first day of your last period).

On the other hand, if you don't want to get pregnant, you should avoid sex during that window, or better yet, use at least one method of birth control every time you have penis-in-vagina intercourse. This not only includes the days leading up to ovulation but on "safe" days during and around your period when the risk of pregnancy, however slight, still exists.

Whether getting pregnant is a goal or something you hope to avoid, it's always a good idea to talk to your doctor. They can help you better understand your body and your cycles, making sex more fun and less stressful no matter what stage of life you are in.

Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. American College of Obstetricians and Gynecologists. Fertility awareness-based methods of family planning.

2. Soumpasis I, Grace B, Johnson S. Real-Life Insights on Menstrual Cycles and Ovulation Using Big Data. Human Reproduction Open 2020, no. 2 (February 1, 2020): hoaa011. doi:10.1093/hropen/hoaa011

3. Wilcox AJ. The timing of the “fertile window” in the menstrual cycle: day specific estimates from a prospective study. BMJ. 2000;321(7271):1259-1262. doi:10.1136/bmj.321.7271.1259

4. U.S. Department of Health and Human Services. Your menstrual cycle.

5. Stirnemann JJ, Samson A, Bernard J-P, Thalabard J-C. Day-specific probabilities of conception in fertile cycles resulting in spontaneous pregnancies. Human Reproduction. 2013;28(4):1110-1116. doi:10.1093/humrep/des449

6. Dasharathy SS, Mumford SL, Pollack AZ, et al. Menstrual bleeding patterns among regularly menstruating women. American Journal of Epidemiology. 2012;175(6):536-545. doi:10.1093/aje/kwr356

7. Cleveland Clinic. Female Infertility.

8. U.S. National Library of Medicine. Pregnancy - identifying fertile days.

By Robin Elise Weiss, PhD, MPH
Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.

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