Basal Body Temperature and Ovulation
The Basal Body Temperature (BBT) method can be used to identify if and when ovulation occurs during your menstrual cycle.
It can be used to understand hormonal changes happening throughout the month and to predict when menstruation will happen when are the most fertile days and investigate potential hormonal imbalances and reproductive issues.
It can also be used for conception or contraception but in this case, it is recommended that tracking happens for at least 2 to 3 months in order to understand your own hormonal variation (which changes for every woman) and other methods are also utilized in conjunction such as the FAM (Fertility awareness method) which includes cervical mucus and position to increase accuracy (Bayley, 2019)
BBT changes throughout the month, and may drop right before ovulation and can increase from 0.2 to 0.5 degrees Celsius immediately after ovulation has occurred and remain high until the next period -until it drops again before menstruation - due to progesterone influence (Flo, 2021)
So how can I take my BBT accurately?
Use a digital thermometer to take your oral temperature at the same time every morning, place the thermometer under the tongue and hold it in place until you hear the beep. It must be done literally first thing in the morning before even talking or engaging in any other activities
Record measurement in a chart or using an app (like Flo or Kindara)
Ideally, you would have had at least 3 hours of sleep before taking the temperature to improve accuracy
Overtime (ideally at least 3 months) the graphs will start to show a pattern that helps determine hormonal variation and if/when ovulation typically occurs (Flo, 2021)
Proper interpretation of the graphs can be tricky when variations are different than what is expected on a normal ovulatory cycle (see figure 1), hence further education or the support of a qualified practitioner is recommended in these cases.
Monitoring cervical mucus can also support understanding the signs of the menstrual cycle. Cervical mucus is present before ovulation and changes appearance and consistency as you become more or less fertile throughout the cycle. You can observe cervical mucus on toilet tissue after wiping, notice the sensation on the vulva as either dry, damp or wet. When the mucus is present you can lift it off the tissue and observe it in between your forefinger and thumb, and then record the findings. The most fertile type of mucus is transparent and stretchy, with a wet, slippery sensation, similar to egg white (Metagenics, n/d).
Figure 1: BBT chart of a normal ovulatory cycle (Bayley, 2019).
References
Clara Bailey (2019). The Beginner’s Guide to the Fertility Awareness Method. Retrieved from: https://www.clarabailey.com/2019/08/30/fertility-awareness-beginners-guide/
Flo (2021). Basal Body Temperature: How to measure BBT to detect ovulation. Retrieved from: https://flo.health/getting-pregnant/trying-to-conceive/tracking-ovulation/basal-body-temperature
Metagenics (n/d). Monitoring Menstrual Cycle signs.
