Your ACTUAL Fertile Window

I can almost guarantee that at some point in your life (particularly your “prime” fertility years) you’ve heard the various warnings about sex and pregnancy. I know I certainly did – I grew up in the Catholic school system (for my elementary years, I shifted into a public high school) where we spent the earlier grades talking about the wonder of pregnancy and how babies were created and then into the later grades either discussing the sin of sex before marriage or, for my grade 8 year, not receiving any sexual health education whatsoever.

My grade 9 and 10 years were equally awful for sex ed – we spent one health class going around the room talking about the different types of birth control everyone was on. And that was it – unless you count the time a public health nurse came in with a variety of objects to have us guess what they represented in terms of sexual health.

The number one myth you’ve probably heard at least once or twice is the good ol’ "sex at any point in your cycle can cause pregnancy". Yikes. That sounds like the gym class in Mean Girls – “if you have sex, you’ll get pregnant, and then you’ll die”.

I need you to read this sentence slowly, and maybe a few times. You cannot get pregnant at all times during a cycle.

Each cycle, you have a fertile window with a start and stop date – it’s approximately 6-7 days in duration. Outside of this window, you are not fertile and will not become pregnant. Fertility tracking methods support the identification of this window so you can either attempt pregnancy or avoid it.

Depending on the fertility tracking method that you use, the accuracy of this window can vary. Methods such as the calendar method and standard dates method (otherwise known as the rhythm method) use set cycle dates to estimate when you are fertile. For example, the rhythm method assumes that days 8-19 are “fertile”. The calendar method, however, requires at least 6 cycles to be tracked before use as it involves comparison between cycle lengths and some math to calculate the fertile window.

The symptothermal method is more labour intensive, but also more accurate, when it comes to identifying your fertile window (hint: it can be slightly different every month, and this is why the pregnancy rate with the rhythm method is slightly higher than other fertility awareness methods).

With this method, basal body temperatures, cervical mucus and cervical height changes are tracked over a cycle. Because these symptoms are taken on a daily basis, they can more correctly identify changes indicating the start and stop of the fertile window.

For ease of understanding, a quick review of ovulation: during the follicular phase of a cycle, a follicle is matured until an ovum or egg is released into the fallopian tube. Eggs are viable for 24 hours after release, whereas sperm can live for 5-7 days after release.

After menstruation stops, the body begins preparation of follicles – this is driven by estrogen. Typically after a period stops there are a few “dry days”, or days where there is no cervical mucus present on underwear or a liner. As estrogen rises in preparation for ovulation, cervical mucus begins to be produced in greater quantities and with gradually changing consistency.

Cervical mucus typically starts with a creamy then more watery consistency, becoming similar to egg whites at its peak fertile status. This fluid’s job is to support sperm in reaching the released egg ASAP. Approximately 24 hours following this peak mucus, it begins to shift back into creamy then dry before a new period starts. Through these changes, cervical mucus can help to predict when ovulation will occur – the start of creamy mucus can be counted as the start of the fertile window.

Basal body temperature also shifts to indicate the fertile window, however it confirms ovulation. Typically temperature has a slight drop followed by a sustained increase. Approximate 4 days of maintained temperature increase indicate that ovulation has been achieved, and may provide some further confirmation that the fertile window has ended.

Cervical height may be additional helpful information, as it shifts higher in the body during ovulation and lower both before, during and immediately after. Each body has slightly different cervical positions and so this is a great bonus for those trying to conceive.

If you’re using a period tracking app, add in these factors to more accurately identify YOUR fertile window and use it to achieve your goals – without the pregnancy misinformation.

Want to learn more? My course, Intuitive Fertility: Master Your Cycle, is an all-inclusive guide to periods, optimizing fertility tracking, and nourishing your cycle. You can register on my Teachable - visit my school Say Yes to Nourish Nutrition to check out curriculum and join the community!