The term “fertile window” describes the period of time in your menstrual cycle when conception is most likely to occur.

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Pregnancy happens when a sperm meets an egg, the egg is fertilized, and that fertilized egg implants into the uterus. A lot of situations need to happen during this process, but timing intercourse during your fertile window can help make conception more likely during any given cycle.

Here’s more about what the fertile window is, what signs you may experience, and how you can use this information to help you get pregnant.

The fertile window is defined as the 5 days leading up to ovulation, the day of ovulation, and the day after. Ovulation refers to the release of an egg from one of your ovaries.

You can estimate this window is by assuming that, following ovulation, the second half of your cycle (the luteal phase) is 14 days long. For people with a 28-day cycle, this means that ovulation may happen around day 14. In this case, days 9 to 15 of the cycle would be considered the fertile window.

The calendar method is a straightforward way to predict the fertile window. It uses an ovulation calculator where you enter the start date of your last period (day 1) and how long your cycle typically is.

Using this information, the calculator sets the day of ovulation for 14 days before the end of the cycle, giving you a general idea of when your fertile window may fall.

You may also have irregular cycles or not ovulate in a predictable way. If this happens, you can try other methods to predict when the fertile window might be, including using ovulation test strips and observing physical signs of ovulation.

The follicular phase is the first half of the menstrual cycle, starting on the first day of bleeding. During this phase, an egg (or eggs) matures and prepares to be released. This phase ends with ovulation.

During ovulation, an egg bursts out of an ovary and then moves down the fallopian tubes to the uterus. If the egg is fertilized by sperm, it may become an embryo, implant into the uterine lining, and grow. This results in pregnancy.

If the egg is not fertilized, it may be discarded from the body when the lining sheds (menstrual period).

Signs of ovulation may be more notable in some people than in others. You may find it helpful to keep a log to observe the individual signs you observe in yourself.

Signs may include:

Timing intercourse around ovulation gives couples the best shot at getting pregnant. Sperm can live up to 5 days inside the female reproductive tract, according to the American College of Obstetricians and Gynecologists (ACOG). The egg can live for 12–24 hours after being released, ACOG says.

So, trying to conceive during the fertile window ensures that sperm will be waiting for the egg.

Some experts recommend intercourse every day during the fertile window. Others say that every other day is enough. Regardless, it takes just one sperm meeting the egg, so sex anytime in the 5 days before ovulation and the day after may lead to pregnancy, per ACOG.

Other ways you can help increase your chances of pregnancy include:

Contact your doctor if these methods do not work within 1 year (if you’re age 35 and younger) or 6 months (if you’re age 35 and above), ACOG advises. Some people need extra support or reproductive technology to get pregnant.

You might consider making a preconception appointment with your doctor. At this appointment, your doctor will review your medical history, discuss genetic health conditions in your family, and give you a physical exam.

Other ways to prepare for pregnancy include:

  • taking a prenatal vitamin that includes 400 micrograms of folic acid
  • exercising regularly, getting around 150 minutes of moderate activity (like walking) each week
  • reaching or maintaining a healthy weight for you
  • quitting smoking, drinking alcohol, and using recreational drugs, if any of these apply to you
  • discussing prescription medications with your doctor
  • avoiding environmental hazards (like chemicals and pesticides)
  • involving your partner in the pregnancy planning process

What day of your cycle are you most fertile?

You are most fertile 2–3 days before ovulation. In a 28-day cycle, this means days 11 and 12 are the most fertile days. Yet ovulation timing may vary between people, depending on the length of your menstrual cycle.

How many days after my period do I become fertile?

It depends. Some people with shorter cycles may be fertile while on their periods or soon after. Others may not be fertile for a week or more after their period has ended.

Can I get pregnant while on my period?

You can have intercourse during your period and achieve pregnancy. Sperm can live for 5 days in the body and can fertilize an egg whenever it is released.

Various factors can affect ovulation, including your individual menstrual cycle, luteal phase length, and overall fertility. That said, using the calendar method to predict your fertile window — combined with observing physical signs — may give you an idea of when intercourse is most likely to lead to pregnancy.