Is it possible to get pregnant during menstruation? This question is very common and can be answered in either the short or long form. Let’s start with the short answer.
Everyone knows that in order to become pregnant, a sperm cell must meet an egg cell, which can only occur during a woman’s fertile period. Therefore, it makes perfect sense to imagine that it is impossible for a woman to become pregnant during her menstrual period, since menstruation is not part of the fertile period of the cycle.
The reasoning above is correct, but the conclusion is wrong. It is possible, yes, to get pregnant if you have unprotected intercourse during your menses. It is neither common nor very likely, but by no means impossible.
So the short and simple answer to the question that gives rise to the title of this article is: yes, it is possible to get pregnant while menstruating.
Let’s now turn to the long answer, which will explain why, although it may seem illogical, it is possible to get pregnant during menstrual periods. Throughout the text we will try to answer and explain the following three questions:
1- Can I get pregnant while menstruating?
2- Can I get pregnant right after my period ends?
3- Can I get pregnant right before the beginning of my next period?
Before we go on with the explanations, let’s talk briefly about the fertile period and fertilization, which is the moment when the sperm meets the egg cell.
Attention, this text only makes sense for women who do not use hormonal contraceptives. If you use the birth control pill, there is no risk of pregnancy during the entire menstrual cycle, even when you take a break from the pill.
Can I be fertile during menstruation?
It is unlikely, but there are special situations in which this becomes possible. These are the cases that lead a woman to become pregnant when she has unprotected intercourse during her menstrual period.
To understand how this is possible, we will explain in a very simple way 4 concepts:
- Duration of the menstrual cycle.
- Time of ovulation.
- Duration of menstruation.
- Fertile period.
Length of the menstrual cycle
The menstrual cycle, also called the ovulatory cycle, begins on the first day of menstruation and ends the day before a new menstrual period. In other words, the cycle begins when menstruation comes down in a particular month and ends as soon as menstruation returns the following month.
In most women, the menstrual cycle lasts about 28 to 35 days. But some people may have cycles that are shorter or longer than this average. Very short or very long cycles are especially common in teenage girls and in women who are close to menopause.
There are women who have a very regular menstrual cycle, with a steady length over the months, while others have irregular cycles, with lengths that vary from month to month.
Timing of ovulation
Regardless of the length of the cycle and its regularity, ovulation usually occurs between 12 and 14 days before the end of the cycle. This means that a woman who menstruates after a 28-day cycle will ovulate around the 14th day. A woman with a 40-day cycle ovulated around day 26, while a woman with a short 22-day cycle ovulated around day 8 of her cycle.
As we will see later, it is women who have a short menstrual cycle who may be technically fertile during menstruation.
Duration of menstruation
Menstruation itself usually lasts from 3 to 7 days. That blood that a woman loses during her menstrual period is actually the inner lining of the uterus that is collapsing, stimulated by hormonal changes from the end of the ovulatory cycle. It is important to point out that the fact that you are menstruating does not mean that your hormonal cycle is stopped waiting for your period to end. On the contrary, the hormonal cycle that will lead to the next ovulation was restarted on the first day of menstruation. This means that on day 7 of your period, your body is already on day 7 of the ovulatory cycle.
The last piece of information we need to know to close our discussion is the concept of the fertile period. We call the fertile period the time interval in which it is possible that an unprotected sexual intercourse will generate a pregnancy.
When a woman ovulates, her egg is viable to be fertilized for only 12 to 24 hours, going up to a maximum of 36 hours in some cases. This does not mean, however, that the fertile period lasts only 12 to 36 hours. Sperm are able to survive in the female reproductive system for 3 to 5 days (there are some that remain viable for up to 7 days, but this is not common). This means, therefore, that the fertile period comprises the 5 days of sperm life plus 24 hours of egg life, i.e. the fertile period is usually 6 days in total.
Situations in which it is possible to get pregnant while menstruating
If you understand everything that has been explained so far, you can probably already imagine why a woman can get pregnant during menstruation. Let’s conclude our explanations with some examples.
Imagine a woman with a short menstrual cycle of only 24 days. If her cycle is 24 days long, this means that ovulation occurs around the 10th day of the cycle. Since we already know that sperm cells usually stay viable for 5 days inside a woman’s body and that the egg cell survives for 24 hours, this means that any unprotected sexual intercourse that has taken place between the 5th and 11th day of the cycle can lead to pregnancy. Therefore, if this woman’s menstrual period lasts 5 to 7 days, it is perfectly possible for her to become pregnant if she has intercourse on the last 2 days of her menstrual cycle (5th through 7th day of the cycle)
Therefore, the shorter the menstrual cycle and the longer the menstrual period, the greater the chances that a woman will get pregnant during her period. Women with a menstrual cycle shorter than 24 days and a menstrual time longer than 5 days are those at greatest risk.
It is important to remember that most women do not have such short cycles or long periods. A woman with a 28-day menstrual cycle and a 5-day menstrual period cannot get pregnant during her period, because her ovulation occurs around the 14th day of her cycle and her period lasts only until the 5th day. Even if this woman has intercourse on the last day of her period, the sperm will only survive until the 10th day of the cycle. When ovulation comes, there are at least 4 days that there will be no more viable sperm to fertilize the egg.
Can I get pregnant in the first days of menstruation?
It is very unlikely, but it is not impossible either. If a woman has an extremely short cycle, about 20 or 21 days long, her ovulation occurs around the 6th day of the cycle, which allows sexual intercourse on the first day of menstruation to still provide viable sperm at the time of ovulation.
This situation is extremely unusual, but again, not impossible.
Is it possible to get pregnant right after the end of menstruation?
As we have already seen, although low, the closer to the end of menstruation, the greater the risk that an unprotected intercourse will generate a pregnancy.
Therefore, a sexual relation that has occurred after the end of menstruation has even more risk than a sexual relation that has occurred within the menstrual period. And this risk increases exponentially as the days go by. A relationship that took place 3 days after the end of your period has more risk than a relationship that took place two days before, which in turn has more risk than a relationship that took place the day after your period ended.
Again, the shorter the cycle and the longer the menstrual period, the greater the risk of pregnancy when having unprotected intercourse right after the end of the menstrual period.
Can I get pregnant right before my period starts?
This is the most unlikely situation of all. For a sexual intercourse that took place 1 or 2 days before menstruation to lead to pregnancy, it would be necessary the simultaneous occurrence of several unlikely situations, such as a very early ovulation and a very high quality sperm that would generate viable sperm for at least 7 days. This is very unlikely.
Therefore, the safest period for unprotected intercourse occurs in the time between the moment the egg degenerates and becomes non-viable (about 24 to 36 hours after ovulation) and the beginning of the next menstrual period. This means a safety interval of 10 to 12 days in women with an ovulatory cycle around 28 days.
The problem is that most women do not know when they have ovulated and cannot be sure of the exact day when their next period will come. Thus, it is very difficult to know when those 10 safest days are to have unprotected intercourse.
- Can You Get Pregnant On Your Period? – American Pregnancy Association.
- Risk of Pregnancy – Princeton University.
- Optimizing natural fertility in couples planning pregnancy – UpToDate.
- Fertility awareness-based methods of pregnancy prevention – UpToDate.