Fertility refers to a person's overall ability to reproduce and create offspring. Broad, right?
There are many factors that impact your overall fertility like: age, smoking status, hormonal (im)balance or exposure to some chemicals. That said, for the purposes of this write up, we are focusing on someone's “fertility window,” the time during their menstrual cycle when conception is more likely to occur.
Historically, the fertile window has been commonly defined as both the day of ovulation and the preceding 5 days based on the seminal work of Wilcox and colleagues… but higher probability of conception have been noted both before and after this range and can be very different for different people (up to 12 days a cycle!).
So how can we track ovulation and its associated impact on likelihood of conception?
Fun fact, some people actually watch changes in their cervical mucus to aid in either avoiding or achieving pregnancy. Cervical mucus is a relatively viscous fluid produced by secretory cells of the cervix. Throughout your menstrual cycle, you’ll notice changes in your cervical mucus related to its colour, texture and amount. To understand how this method works, we are going to take a quick look at the science behind cervical mucus monitoring.
At the end of Phase Two, we know that estrogen levels have reached their peak and set off a chain reaction of different hormones and events that lead to ovulation. The rise in estrogen levels also supports the secretion of clear (or mostly clear), stretchy (approximately 1 inch), and/or slippery (lubricative) discharge known as estrogenic cervical mucus or “peak type” mucus.
The thinking around monitoring cervical mucus goes like this: you start to notice this type of cervical mucus as your estrogen levels peak near the end of Phase Two. Then you monitor for this specific type of cervical mucus and on the last day you observe any mucus discharge that is “peak type” is assumed to be the day of ovulation. Past research has shown that the days with peak type mucus have the highest fertility potential and give an estimate of our ‘most fertile’ days. To be clear, this does not mean you are not fertile on other days, you can definitely still get pregnant on days without peak type mucus.
There is still a lot to learn about how cervical mucus could be leveraged in understanding our bodies. Current tracking methods (and the “expected outcomes”attached to them) might work better for some women than others as some women don’t ever seem to experience peak type mucus, some experience multiple starts and stops of this type of mucus (suggesting multiple times of ovulation).
Fertility and fertility monitoring is not a one size fits all, and while there is some great general advice out there, if your goal is to get pregnant it might be worth a call to your doctor to get some personalized care.
Najmabadi, S., Schliep, K. C., Simonsen, S. E., et al., (2021). Cervical mucus patterns and the fertile window in women without known subfertility: a pooled analysis of three cohorts. Human reproduction (Oxford, England), 36(7), 1784–1795.
