Can You Get Pregnant on Your Period?

Vilma Ruddock

"Can you get pregnant on your period?" is a common question from women. The answer is, it's possible. If you are still menstruating near mid-cycle when ovulation occurs and have intercourse, you can conceive.

Can You Get Pregnant on Your Period?

Your egg can fertilize if you have unprotected intercourse on any of the days you are most fertile in your menstrual cycle, even if you are still bleeding. Note that in this situation, the pregnancy is less likely, but not impossible, to implant in your uterus.

Understanding Your Period and Ovulation

During each menstrual cycle, estrogen and progesterone from the ovaries prepare the uterine lining (endometrium) for a pregnancy. If the egg doesn't fertilize and develop to a fetus, the lining sheds as a period and a new cycle starts.

A 1995 New England Journal of Medicine study gives insights into the most fertile time in a woman's menstrual cycle - when she is most likely to conceive, bleeding or not. This fertile window is based understanding the timing of ovulation and the lifespan of the egg and sperm. If you have the average 28-day menstrual cycle:

  • You ovulate on about day 14 of you menstrual cycle.
  • Your six-days fertile window starts five days before and ends on the day of ovulation. This is means you are most fertile on days nine to 14 of your 28-day cycle.
  • Because sperm can survive in your reproductive tract for up to five days (sometimes longer), you can get pregnant even if you have intercourse on only one of those six days, starting on day nine.
  • If your period is just the average five days long, you are unlikely (not impossible) to get pregnant if you have unprotected intercourse only up to day five of bleeding.
  • If however, your period lasts longer than five days and you are still bleeding on any of the fertile days and you have unprotected sex, you are more likely to conceive.
  • Even with a regular 28-day cycle you may sometimes ovulate earlier than usual in the cycle. In that cycle, your fertile days will start before day nine while there is a chance you are still bleeding.

Shorter Menstrual Cycles

If your cycles are shorter than 28 days, you will ovulate before day 14 and therefore are more likely to be still bleeding near ovulation. For example, if your cycles are 24 days long, you might ovulate about day ten. Your fertile days would be between days five to ten. You can get pregnant if you have sex on day five, for example, while you are still bleeding.

Important to Know

It is important to know that if your endometrium is still shedding near ovulation, it might not be fully prepared to accept the fertilized egg (early embryo) for normal implantation when it reaches the uterus. You might end up with a chemical pregnancy or a non-viable early embryo.

Be aware also that having unprotected sex during your period increases your risk for acquiring a sexually transmitted infection, which will be a bigger problem if you conceive.

Calculating Your Cycle

You can use a menstrual cycle chart to keep track of your cycle for at least three months to help you calculate when you ovulate. No matter how long or short your cycle or your period, your ovulation occurs 12-14 days before your next period. An online fertility calculator can also help you to estimate your day of ovulation.

In addition, you can observe signs of fertility each cycle to keep track of when you are most fertile. This will help you avoid getting pregnant or increase your chance of conception if that's your aim.

Bleeding Between Periods

Sometimes, irregular bleeding might make it difficult to figure out the menstrual cycle and which bleeding episode might be the real period. Several hormonal disorders, including those of the pituitary, thyroid, and ovaries, as well as other health problems, can cause irregular menstrual cycles and bleeding between periods.

The irregular bleeding can make it confusing to know if or when you are ovulating and when you are most fertile. If you can't estimate your day of ovulation, you are more at risk for an unplanned pregnancy if you have sex while bleeding.

Preventing Pregnancy During Your Period

It's possible to get pregnant during your period if you have unprotected sex close to ovulation. If you don't want to get pregnant, be sure to use adequate protection if you choose to have intercourse during your period or other bleeding. Condoms and spermicides, although not 100 percent effective, would be the appropriate choice if you are not on other birth control. It also has the added benefit of decreasing your risk for an infection. Talk to your doctor about a more effective method of contraception if you want to avoid an unplanned pregnancy.

Can You Get Pregnant on Your Period?