You typically have a narrow window in which you can become pregnant. It may be possible to become pregnant in the days before your period, but it can depend on certain factors.

Although it is possible to get pregnant in the days leading up to your period, it isn’t likely.

You can only get pregnant during a narrow window of five to six days a month.

When these fertile days actually occur depends on when you ovulate, or release an egg from your ovary.

Ovulation usually occurs in the middle of your menstrual cycle — about two weeks before your period — but not everyone’s cycle is regular.

Even for those with a regular cycle, it’s possible to ovulate earlier or later. This can shift the fertile window by a few days in a given month.

In other words, it’s difficult to pinpoint a time in your cycle where you can 100 percent guarantee that you will or won’t get pregnant.

Chance of becoming pregnantIt’s unlikelyIt’s possibleIt’s likely
14 days beforeX
10 days beforeX
5–7 days beforeX
2 days beforeX
1 day beforeX
During menstruationX
1 day afterX
2 days afterX
5–7 days afterX
10 days afterX
14 days afterX

The average menstrual cycle is 28 days, with the first day of menstruation as cycle day 1.

Most periods last two to seven days. Pregnancy is uncommon during this time, because your peak fertility window is still about a week or so away.

Around days 6 to 14 of your cycle, your body will start releasing follicle-stimulating hormone (FSH).

This helps develop an egg inside your ovary. Your body will also begin rebuilding the endometrial lining in your uterus.

Pregnancy is slightly more likely during this time. Sperm can live up to five days inside the body, so it could still be present when the egg matures.

Once the egg is mature, your body will release lutenizing hormone (LH), triggering the egg’s release from your ovary (ovulation).

Ovulation usually occurs around cycle day 14. Pregnancy is likely on ovulation day.

That said, ovulation doesn’t always happen like clockwork. It can occur anywhere from four days before to four days after the midpoint of your menstrual cycle.

The bottom Line

If you ovulate later in your cycle or start your period sooner than usual, you could become pregnant if you have sex in the days leading up to your period.

Lots of people don’t have 28-day cycles. Some have cycles as short as 21 days and others as long as 35 days.

In fact, in one study, only about 30 percent of participants had their fertile window fall within days 10 to 17 of their cycle. Only 10 percent had ovulation fall exactly 14 days before their next period.

Stress and diet can also impact when ovulation occurs, as well as medical conditions such as polycystic ovary syndrome (PCOS) and amenorrhea.

Menstrual cycles can also be more irregular during adolescence or perimenopause.

In many cases, ovulation still happens around the middle of your cycle.

Try this

If you’re trying to figure out when you might be ovulating, a good place to start is by determining the midpoint of your individual cycle.

But if your cycle length varies from month to month, it may be helpful to use a backup birth control method.

If you’re trying to get pregnant, you might consider formally tracking your ovulation. This can provide a more reliable view of your fertile window.

You can do this a number of ways, including:

  • tracking your basal body temperature
  • using an over-the-counter ovulation predictor kit
  • wearing a fertility monitor

The only time you can get pregnant is during your fertile window.

An egg only lives for about 24 hours after being released from your ovary, and sperm can only live for up to five days inside the body.

That means you can only get pregnant if you have sex:

  • in the four to five days leading up to ovulation
  • on the day of ovulation
  • on the day after ovulation

If you’re looking to conceive, the best time to have sex is right before ovulation. This will give sperm time to reach the fallopian tube and meet the egg there.

After that, if no sperm has fertilized the egg, it will dissolve. You won’t be able to get pregnant until your cycle restarts.

It isn’t impossible, but it’s unlikely. The timing would have to be perfect for the egg and sperm to reach each other in time.

If you have sex toward the end of your period and you ovulate early, it’s possible for the egg and sperm to both be alive at the same time and for fertilization to occur.

It’s unlikely — though slightly more likely than if you have sex during your period.

If you have sex right after your period and you ovulate early that month, it’s possible to get pregnant.

This is more likely with people who have a shorter-than-average cycle, because ovulation occurs more frequently.

Your period will only start if the egg isn’t fertilized and the cells are reabsorbed.

This causes estrogen and progesterone levels to fall and menstruation to begin.

However, you may experience some spotting during early pregnancy.

One study found that 14 out of 151 participants experienced one day of vaginal bleeding in the first eight weeks of pregnancy.

Furthermore, 15 percent to 25 percent of people may experience spotting during the first three months of pregnancy.

Taking note of the timing and any other symptoms present can help you differentiate between typical menstruation and pregnancy-related spotting.

Implantation bleeding usually occurs 6 to 12 days after conception. It’s caused by the fertilized egg attaching to your uterus lining.

This light spotting usually only lasts 24 to 48 hours and is generally much lighter than the average period.

You may also experience spotting as a result of increased blood flow in the cervix. This type of spotting is most common after sex, a Pap test, or a pelvic exam.

If you’re experiencing unexpected bleeding, see a doctor or other healthcare provider.

If you had unprotected sex and want to avoid pregnancy, take emergency contraception (EC) as soon as possible.

There are two main types — the copper IUD and the hormonal EC pill — and they can both work up to five days after unprotected sex.

The IUD prevents pregnancy by producing an inflammatory reaction that’s toxic to sperm and eggs.

It’s more effective than the morning-after pill, but it’s only available by prescription and has to be inserted by a doctor within five days of unprotected sex.

The pill delivers a high dose of hormones to delay ovulation or prevent a fertilized egg from implanting to the uterus.

Plan B One-Step, Next Choice, and MyWay are all available over the counter.

Which should you use?

As a general rule of thumb, EC pills may be less effective for people who have a higher body mass index (BMI).

There isn’t any research to suggest that the copper IUD is similarly affected by BMI, so this option may be more effective.

Talk to your local pharmacist or other healthcare provider about which EC option is right for you.

Wait until the first day of your missed period to take a home pregnancy test.

But if you can wait a little longer, taking the test one week after the date of your missed period may produce the most accurate result.

If you have an irregular cycle, wait one to two weeks after you had sex to take the test.

This will allow your body to develop high enough human chorionic gonadotropin (hCG) levels to be detected by the test.

If you get a positive result, you might want to check again in a day or two since it’s possible to get a false positive. Then reach out to a medical provider to confirm the results.

Whether you’re trying to prevent pregnancy or trying to conceive, it’s always a good idea to talk about it with a doctor or other healthcare provider.

They can help you learn more about your cycle and discuss your options moving forward. This could include birth control, fertility awareness, or family planning.

Simone M. Scully is a writer who loves writing about all things health and science. Find Simone on her website, Facebook, and Twitter.