By tracking your menstrual cycle carefully, you can reduce the risk of pregnancy by avoiding unprotected sex during your most fertile days every month. On average, the 5-7 days leading up to and including the ovulation day are the most fertile, the days you are most likely to get pregnant.

Using Cycles to determine your most fertile days

You can determine when you’re most fertile every month by tracking physical symptoms, and using the days of your period to determine when you’ll ovulate next. A woman ovulates once per month, usually around day 14 in a 28 day cycle (day 1 being the first day of her period), and it is only during the days around her ovulation day that she can become pregnant.

Note: Fertility awareness does not protect you from contracting STIs and is never completely effective in preventing pregnancy.

However, when used together, the various fertility tracking methods can become more effective in determining your ‘fertile window’. Here are the three main fertility tracking methods:

The Temperature Method

This method requires that you take your basal body temperature to determine when you’re ovulating, as your body temperature rises slightly right after ovulation. In order to anticipate this day for your next cycle, you should take your temperature when you first wake up in the morning, every day. Then, when you’ve determined what day of the month it is, you can plan to avoid unprotected sex during the 5-7 days leading up to and including your ovulation day (the fertile window).

You can then record your BBT logs in Cycles to create a clear graph showing your ovulation date.

The Cervical Mucus Method

Cervical mucus changes in consistency and color depending on if you are ovulating, when ovulation is very close and after ovulation has finished. Paying attention to the consistency of cervical mucus can help you track when you’re most fertile. Here are some of the consistency types and what they mean:

• Not ovulating: Dry and sticky
• Ovulation is very close: Wet and watery
• Ovulation may be coming: Creamy
• Ovulation: Wet and stretchy, resembles egg whites

The Ovulation Test

The test measures your luteinising hormone levels (LH) and can be purchased in most pharmacies. To help determine when you are ovulating, start taking ovulation tests on day 11 of your cycle (11 days after the first day of your period) and continue until you notice the LH levels rise. When you notice your LH levels have risen, ovulation will typically occur 20-48 hours after, helping you determine whether you’re right about which day you ovulate every month.

How effective is fertility awareness?

It can be very effective when followed perfectly, but this method requires commitment, practice and a thorough knowledge of your body. The effectiveness can range depending on how well you track your period or the fertility awareness method you choose, but it is generally somewhere between 76-88% effective.

If you're considering using fertility tracking as contraception, it's a good idea to arrange an appointment with your healthcare provider so you can learn exactly what to track and when.

Note: your ovulation day can vary between cycles based on factors like stress, sickness, exercise and more. This is why no period tracker can say with 100% certainty when your ovulation will fall each month, and shouldn't be used a sole method of contraception.

That said, there are ways to get more accurate fertility predictions in Cycles. For example, if you consistently log your BBT, CMQ or ovulation tests, your fertility accuracy will improve.