What are the Odds of Getting Pregnant on Your Period?

Is it possible to conceive while menstruating? Can sperm survive in blood? Fertility expert and OBGYN Dr. Gleaton gives us the 4-1-1.

By OBGYN and fertility expert Dr. Kenosha Gleaton

Whether you’re trying to conceive or not, it’s helpful to know how to plan around your fertile days and not-so-fertile windows. Let’s talk about how menstruating can impact your chances of conceiving.

Can You Get Pregnant While On Your Period?

Contrary to common belief, it's not impossible to get pregnant during menstruation, but it's quite unlikely.

The chance of conception hinges on the timing of ovulation day and the lifespan of sperm. Sperm can survive up to five days in the female reproductive system.¹ If you have sexual intercourse towards the end of your period and ovulate early, especially if you have a shorter or irregular cycle, conception is possible. However, remember that what may seem like menstrual bleeding could sometimes be implantation bleeding, causing potential misinterpretation of your fertility window. While the probability is low, understanding your cycle and prioritizing sexual health by employing appropriate contraceptive methods can effectively manage these odds.

Likelihood of Getting Pregnant While Menstruating

Based on a typical 28 day average menstrual cycle, it’s extremely unlikely to get pregnant while menstruating. The period marks the first day of a new cycle, and the fertile period starts around day 9-14.²This means that for pregnancy to occur, you’ll need to have sex during the fertile window as sperm can only live inside the reproductive tract for around five days.

Of course, there are individuals who may experience irregular periods and determining the fertility window may be a bit challenging.

The chances of conceiving on the first few cycle days of your period are when it is the most unlikely to conceive, although the likelihood does increase towards the end of the menstrual period.

How Does Getting Pregnant on Your Period Occur?

In order for pregnancy to occur, sperm has to fertilize a mature egg. If you only had sex on your period and still got pregnant, this may point to a few things:

• You have a short menstrual cycle: Typically ovulation occurs 14 days before the period, but menstrual cycles can be different for everyone and are sometimes irregular, or shorter than the usual 28 day cycle. It’s possible that you have a shorter cycle, closer to 20 days, and ovulate only a few days after your menstrual period ends. Sperm can live inside the reproductive tract for up to five days, creating some overlap between the final day of your period and the period of ovulation period. Thus, even if a woman experiences a shorter cycle and has sex during her period, sperm from ejaculation may remain inside her reproductive system and may fertilize the egg if ovulation occurs.
• That blood wasn’t from your period: If you experienced some bleeding that you assumed was your period, it’s possible it could’ve been implantation bleeding. It’s normal to have a little bit of spotting after a fertilized egg burrows into the uterine lining. Taking a pregnancy test too soon after implantation or before implantation has actually occurred can result in a false-negative result. However, waiting seven days after implantation is likely to yield an accurate result.³

So while the chances of getting pregnant from period sex are low, there are still some factors that can increase the chances. A shorter cycle, irregular menstruation, and spotting are just a few factors that can play a role.

Can Sperm Survive in Menstrual Blood?

Yes, sperm can survive in menstrual blood. Sperm can survive in the reproductive system during the five days prior to and the day after ovulation, regardless of if menstruation is occuring.

What’s Ovulation Anyway?

Ovulation is the release of an egg from the ovary and occurs typically 14 days prior to the next cycle (menstruation). Ovulation is triggered by a surge of Luteinizing Hormone or LH and typically occurs within 48 hours of this surge. The ovary releases an egg which travels into the fallopian tube and toward the uterus.

The lifespan of a released egg is only 24 hours, and if not fertilized during this time, it will die. Ovulation is detectable in the urine using ovulation tests, which measure LH levels and can be useful in timing intercourse when trying to conceive. Although pregnancy can occur during the five days prior to and the day after ovulation, you are most likely to conceive if sperm are swimming in the fallopian tubes prior to ovulation occurring. 

How To Reduce the Chances of Getting Pregnant

If you’re not trying to conceive, there are a lot of ways to reduce your chances. Birth control comes in many forms. Here’s a quick breakdown:

Hormonal options

• Birth control pills: Either combination pills or progestin only
• Birth control shot: Given every three months
• Hormone patch: Changed once a week
• Implant: Inserted under the skin of the arm, provides protection for up to four years
• Hormone vaginal ring: Changed once a month/every three weeks

Barrier options

• Condoms: male or female
• Diaphragm/cervical cap: An object placed inside the vagina to block sperm from reaching an egg, usually used with a spermicide
• Spermicide: Can be a gel, foam, or other substance made for killing sperm before they can reach an egg

Intrauterine options

• Copper IUD: A device inserted into the uterus that can last up to 12 years
• Hormonal IUD: A device inserted into the uterus that can last up to six years

Permanent options

• Tubal ligation: This is a medical procedure that blocks the fallopian tubes so that no eggs can be fertilized
• Vasectomy: This is a medical procedure that blocks sperm from mixing with semen so that no eggs can be fertilized.

Other options

• Lactational Amenorrhea Method (LAM): This may work for women who have recently had a baby and are breastfeeding—although it’s not always a reliable method—and certain simultaneous conditions must be in place: (1) the baby is under six months, (2) the mother is still amenorrheic, and (3) the mother practices exclusive or quasi-exclusive breastfeeding on demand, day and night.
• Emergency contraception: There are two immediate contraception methods available if you’re in a pinch. The copper IUD can be inserted up to five days after unprotected sexual intercourse, or plan-B can be taken up to three days after unprotected sex (although taking it sooner = better chance of it working).
• Fertility awareness-based methods: There are a lot of methods that fall under this category, including tracking ovulation, tracking cervical vaginal mucus, body temperature, and more. Read more about natural family planning.

Key Takeaways

• The typical cycle lasts 28 days, but can vary depending on the person.
• While it’s still not very likely, you have a better chance of conceiving towards the end of your period than on the first few days.
• If you had sex on your period and are pregnant, you may have a short cycle, or you may have confused implantation bleeding for your period.
• Ovulationoccurs around the middle of your regular cycle, about 14 days before your period begins.
• A released egg has about 24 hours to be fertilized before it dies, so if you’re TTC, you’ll want to have sex in the days leading up to ovulation.
• Sperm can live in the reproductive tract for up to five days.
• There are many options to reduce the chance of getting pregnant, including hormonal birth control, barrier methods, intrauterine devices, and more.

Sources:

1. Gargollo, M.D. P. Sperm: How long do they live after ejaculation? Mayo Clinic. Published May 5, 2022. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/expert-answers/pregnancy/faq-20058504
2. Stirnemann JJ, Samson A, Bernard JP, Thalabard JC. Day-specific probabilities of conception in fertile cycles resulting in spontaneous pregnancies. Hum Reprod. 2013;28(4):1110-1116. doi:10.1093/humrep/des449
3. Chard T. REVIEW: Pregnancy tests: a review. Human Reproduction. 1992;7(5):701-710. doi:https://doi.org/10.1093/oxfordjournals.humrep.a137722
4. Vekemans M. Postpartum contraception: The lactational amenorrhea method. The European Journal of Contraception & Reproductive Health Care. 1997;2(2):105-111. doi:https://doi.org/10.3109/13625189709167463