When Is the Fertile Window?


If you’re trying to get pregnant, knowing when you are most fertile is incredibly important. The so-called “fertile window” falls in the 2-3 days preceding ovulation. Having sex on the days of your fertile window gives you the greatest chance of getting pregnant.

But before we dive into the fertile window, let’s recap what happens when you ovulate.

Ovulation: What Is it?

During reproductive ages, the ovary releases an egg every month. This event occurs when ovary follicles rupture and release the oocyte which travels to the fallopian tube and becomes an ovum

The rupture of the ovary follicles can cause some light spotting and some can even feel it happen in their body. After the oocyte is released from the ovary, it moves into the fallopian tube. At this point it is called an ovum . The egg stays in the fallopian tube for about 24 hours, waiting for a single sperm to fertilize it.

If the egg is not fertilized by sperm during that time (and pregnancy does not occur), it disintegrates (breaks down) and menstruation (your menstrual period) begins 11-16 days later.

It's worth noting that a man's sperm can live between three and five days after sexual intercourse. This means that even if you’re not ovulating when you have intercourse, the sperm can still fertilize your ovum up to five days later, resulting in pregnancy.

Understanding Your Fertile Days

If you want to get pregnant or to learn more about when you're fertile it really starts with understanding your entire menstrual cycle. Most women are acutely aware of their period (the first day of your period is Day 1 of your cycle), but they may be less familiar with the other events.

The first day of your menstrual cycle is counted from the first day of your period and ends at the beginning of your next period. The average cycle length is 28 days. Ovulation is a key even and it occurs on approximately Day 14 of an average 28-day menstrual cycle.

Your most fertile days ("the fertile window") are the 3 days leading up to and including ovulation. This is when getting pregnant is most likely. So, having sex then gives you the best chance of ensuring the egg is fertilized by sperm so pregnancy can occur.

How to Know When Your Fertile Window Occurs

Ovulation tests can be a useful tool for those trying to conceive and wishing to identify the best time to try to get pregnant. You should start testing  3 days before your expected ovulation day.

These tests identify the LH surge (luteinizing hormone) that happens 24-36 hours before ovulation. It’s important to factor in that sperm can survive in a woman’s body up to 5 days, so if you have sex before you ovulate, there can still be sperm present to fertilize the egg.

Every woman’s cycle is different. Some of us have longer periods than others, for example. So the timing of when you ovulate  is not always the same for every woman.

So, if your average cycle is 28 days and the first day of your cycle is Day 1 of your menstrual period, day 14 in your cycle is your day of ovulation, and your most fertile days are days 12, 13 and 14. These are the days pregnancy is most likely to occur and when you should start testing with an ovulation calculator or test.

And if your average cycle is 35 days ovulation happens around day 21 and your most fertile days are days 19, 20 and 21 and these are the days when you should start testing with an ovulation calculator or test in order to increase your chances of pregnancy.

Other Signs & Symptoms of Ovulation

Ovulation usually goes unnoticed in many but there are some symptoms that most women can learn to track or pay attention to understand their fertile window.

Your Basal Temperature Falls

One of the most objective symptoms is that your basal body temperature drops a little bit just before your egg is released from your ovary. Then, 24 hours later, your basal temperature rises and stays up for several days. If you're trying to get pregnant, it's advisable to take your temperature to understand when you're ovulating.

According to Healthlink BC your Basal body temperature averages between 36.1°C (97°F) and 36.4°C (97.5°F) before you ovulate. It averages 36.4°C (97.6°F) to 36.4°C (97.6°F) after you ovulate. 

Discharge Changes When You Ovulate

The changes in your cervical mucus over the course of your menstrual cycle also hold clues about when you might be ovulating.

If your cervical mucus is...

  • Dry or sticky: It’s unlikely you’re ovulating
  • Creamy cervical mucus: Ovulation may be coming
  • Wet or watery: Ovulation may start soon
  • Wet and stretchy (eggy white texture): You may be at your day of ovulation

Your Cervix Softens and Opens Up

As you approach your most fertile time, your cervix softens. This is sometimes known as having a short, high, open and wet cervix. 

For a step-by-step guide to checking your cervix position, visit this guide on Flo’s website

You May Experience Slight Twinge or Cramping

Mittelschmerz translates literally as “middle pain” and is the name for the slight twinge or cramp that some women experience when the follicle releases the egg on the day of ovulation during your menstrual cycle.

Some Light Spotting May Occur When You Ovulate

When the ovaries release the egg, a tiny follicle ruptures to allow the egg to be released. This can be a cause of spotting for a day or so.

For some women, spotting that occurs around the time of ovulation is light red or pink in color. This is because we also produce more cervical fluid around the time of ovulation and the blood gets mixed with that fluid, causing it to be a lighter shade.

Increased Libido or Sex Drive

The most well-known sign of ovulation is an increased sex drive. It’s important to know that this does not mean you’ll only want to have sex during ovulation. But it may definitely mean that you may experience an increased libido when ovulation occurs.


Learning about your fertile window and tracking when it occurs can be an important step if you’re planning to get pregnant. Ovulation tests give you a good ability to predict the best days to conceive. However, there are other symptoms which you should also monitor and track to understand your fertile window.

Not only will being aware of these give you increased familiarity with your own menstrual cycle, it will also give you good information to discuss with your doctor if you have any issues becoming pregnant.