How to Track Fertile Days in Your Period Cycle

Marie-Claire De Villiers
By Marie-Claire De Villiers
Head and Shoulders Photo of Michelle Meyer
Edited by Michelle Meyer

Published August 3, 2022.

Woman holding mobile phone with one hand and a packet of pills in the other hand

When you're keen to conceive - or even to avoid conception - it's helpful to have a mental picture of what's happening to your body through the menstrual cycle and to know the signs of your fertility.

There are four different phases of the menstrual cycle:

  • Menses - the temporary extra lining of the uterus comes away (the endometrium) and is shed in a menstrual bleed lasting about two to seven days.
  • Follicular phase - preparation for conception occurs as hormones trigger the release of a new ovum from the fallopian tubes, any time from 7 to 14 days from the first day of menstruation. The hormones also cause the uterus to develop a new endometrium for cushioning and nourishing.
  • Ovulation - the ovum is available for fertilization by healthy sperm in this ideal uterine environment. This phase provides a window of opportunity for conception and is about two fertile days.
  • Luteal phase - the ovum changes and is now called the corpus luteum or body of the egg. It releases more powerful hormones to trigger a richer environment in the uterus, but deteriorates if it's not fertilized by sperm within two days. If there is no fertilized corpus luteum attaching itself to the wall of the uterus, the thickened lining gradually begins to dissolve, and fertility is no longer possible in this cycle. Your body then prepares to get rid of these byproducts of fertility with a new menstrual flow.

What Are the Signs of Ovulation?

If you want to know when and whether you are ovulating, these are the signs of ovulation you need to attend to:

  • after menstrual bleeding has stopped, your normal vaginal secretions change from being scanty, then watery and thin, to being thick, clear, and stretchy, like egg white, at about day 7 to day 10 of your cycle;
  • your breasts may feel very sensitive;
  • you may observe some low abdominal cramps like menstrual cramps as the ovum is released from the fallopian tube;
  • you may experience some abdominal bloating, usually linked to these cramps;
  • you may feel a heightened sense of sexual awareness and desire, which is a result of your hormones working to facilitate conception; and
  • your basal body temperature rises by about two degrees at ovulation and can be measured with a fertility thermometer.

If you are not fertile, you will notice none of these signs, because they all rely on the luteinizing hormone, which is the main facilitator of fertility. The most easily observed sign is the clear, stretchy vaginal mucus.

Fertile Days in Your Period Cycle

All of these fertility signs are present for only about a two-day window period where you are most fertile. However, you can get pregnant if you have sex during the last days of your period because sperm lives for up to five days in the uterus. Your period may stop, and you may ovulate within those five days.

Therefore, you can theoretically fall pregnant at any phase of your cycle. The varying factors include how long your menstrual cycle lasts, when you ovulate in a particular month, and how long the sperm may stay viable. Some men's sperm may be stronger swimmers or denser, making fertilization in the uterus likelier, even a few days after having sex. You may also fall pregnant more easily if you are within a profile of young and healthy women.

To help you find out if you're pregnant, you should use a pregnancy test rather than an ovulation test, and be aware that it is most accurate two weeks after having sex, rather than immediately.

How to Track Your Fertile Window

The best way to track your fertile window is by monitoring the signs of ovulation either manually or by using a device for cycle and ovulation tracking.

Can You Get Pregnant While on Your Period?

This is possible but unlikely, because of the flow of blood and the discarding of the endometrium which a fertilized egg needs to attach to in order to grow. The conditions during your period are not as positive for conception as the ideal conditions during ovulation. However, with all the uncertainties at play in your body and your life, it's still possible.