Signs of Fertility: What your body can tell you about your fertility

In biology class you may have learned about your reproductive organs and hormones, but it’s unlikely that you learned about how your cervical fluid, temperature, urine and saliva all can be used to indicate your fertility. Women can learn about their unique cycles using their own physiological signs to predict and determine ovulation.

Ovulation calculators are often used when women are trying to conceive to figure out the fertile window. To use, you need to know the length of your menstrual cycle, which is from the first day of bleeding to the first day of bleeding in the next period. For example, if your period started August 10th d and then the next one started September 7th, your cycle is 29 days long. Once it’s known how many days your average cycle is, subtract 14 days from the end of the average length and that is the approximate day of ovulation. So, if your period started September 7th, it would be estimated that you would ovulate on the 22nd of September.

This is simply an educated guess, however, not actually when you ovulate. A study by Wilcox et al found that only 30% of women were fertile between days 10 and 17. Women in the study reached their fertile window earlier and others much later than the ‘14-day’ estimate. Which is why you should use physical biomarker(s) to truly pinpoint your own unique ovulation cycle.


As your body prepares for ovulation, your cervical mucus changes. This change makes it so the sperm can live longer inside of you as well as get to your fallopian tubes where they need to reach the egg. If you are not in your fertile window, your cervical mucus may not allow for the sperm to get through.

Cervical fluid reveals much more about our bodies than meets the eye because the consistency changes under the influence of rising levels of estrogen. After having a period, women typically experience low levels of estrogen which results in non-wet secretions, or what is called ‘dry days’. As estrogen levels rise, the fluid changes to a wetter consistency as she gets closer to ovulation.

You can learn more about how to track your cervical fluid


Ovulation Predictor Kits measure hormonal changes to predict the days before ovulation and the day of ovulation. Products you can use at home typically require either urine or saliva samples. There is a hormone in your body called the luteinizing hormone (LH) that rises one to two days before you ovulate. Urine ‘pee sticks’ detect LH and some detect both LH and estrogen. LH will raise two days before you ovulate and estrogen increases a couple of days before the LH surge. To use OPKs using urine, you urinate on a LH test stick that notifies you whether or not there is a surge in the hormone or not.

Saliva tests are observed under a small portable microscope. As you approach the time of the month when you are most fertile, the level of the hormone estrogen increases in your body. As the estrogen surge intensifies, so does the concentration of electrolytes (salinity) in your saliva. This is the cause of the crystal ferning patterns that indicate that you may be about to ovulate.

When it’s time, your dried salvia may form a fern shaped pattern to indicate that you are fertile. To use, you smear saliva onto a slide and then observe it through a microscope. Your saliva produces a ferning pattern that becomes more obvious closer to ovulation due to the increase in estrogen. Test results are compared to pictures that come with the kit.


Basal Body Temperature

Temperature is another biomarker to indicate ovulation is about to occur or has occurred. A method referred to as the BBT Method measures your Basal Body Temperature (your temperature when you are fully at rest). This requires you taking your temperature every morning and charting it either with an app or on paper. Vaginal temperature is the most accurate, however, you can use oral or ear temperature thermometers. Once you ovulate there is a rise in temperature indicating that you have ovulated. BBT can’t predict your fertile window, but it can give you some sense of when you ovulate for the next month and if you are ovulating.

You can manually chart your temperatures or use a charting app. When your temperature rises, this indicates that you may have ovulated. The luteinizing hormone surge, which stimulates ovulation, is associated with a 0.5- to 1°F- (0.3- to 0.6°C-) rise in BBT measured with highly standardized methods. BBT remains elevated throughout the luteal phase secondary to higher progesterone levels. The woman is assumed to have ovulated after observing 3 consecutive days of temperature elevation.

Continuous Core Temperature

Continuous core temperature can reliably detect a pre-ovulatory shift that occurs 24-48 hours prior to ovulation (Coyne 2000). While BBT can only tell you after you have ovulated, continuous core temperature measurements can be an important tool for predicting ovulation.

Women’s bodies tightly control body temperature and exhibit a striking temperature patterns that change with their hormones. This temperature pattern has been well studied and has been established as a highly reliable marker for circadian rhythm (Brown 2000).

If you are unsure of when you ovulate, you don’t need to be anymore. Pick a method that works best for you: some women enjoy tracking their BBT and find it easy, while other women find it stressful and too hard to remember to do daily; some women find LH kits easy read and use and other find them confusing and unreliable. Regardless of what method you decide works for you, be sure to have intercourse every day or every other day PRIOR to ovulation.