Basal body temperature (BBT) is the “lowest natural, non-pathologic body temperature recorded after a period of rest” (Steward & Raja, 2023). The purpose of BBT charting is to track a woman’s unique temperature patterns over the course of multiple menstrual cycles. This information is often used in conjunction with other fertility tracking methods to either prevent pregnancy (by abstaining from unprotected intercourse during a specific time period) or to determine if ovulation has occurred or not in hopes of becoming pregnant.

Ovulation is the short period of time (usually 2-4 days) in a woman’s cycle when she is able to conceive. This is when a mature egg is released from the ovary and moves into the Fallopian tube where it can be fertilized by a sperm.

Shortly after ovulation occurs, BBT charting should indicate a “noticeable increase of approximately 0.5 to 1 degrees F” which will remain high for the remainder of the cycle but will eventually return to baseline at the onset of menstruation (Stewart & Raja, 2023). This increase in temperature is due to increased levels of the hormone progesterone which is released after ovulation and acts upon the hypothalamus to set a higher body temperature. If you are using the BBT method as a way to get pregnant you should start having unprotected sex from when your period ends until the time at which your BBT shows an increase as women will be most fertile during the 2-3 days prior to their temperature spike.

How to Chart BBT:

1. Take temperature at the same time every day
2. Take temperature immediately after waking up
3. Record temperature prior to eating or drinking
4. Ensure that you move as little as possible prior to taking temperature

It is important to note that BBT is usually used in combination with other fertility tracking methods. Alone, it is not the best way to prevent pregnancy as there are many other factors that can influence BBT (ie. illness or fever, stress, shift work, alcohol, certain medications, + more).

BBT tracking can be done using paper and pencil and a regular thermometer or you can create or download a fillable tracking form online. It can also be done using an app like Premom (no affiliation). Premom is a great option because it can be used with their ovulation test strips to get a more accurate idea of when and if ovulation is happening (see below for links to all products mentioned)

Here is an image from Premom.com that illustrates BBT temperatures (in blue) in conjunction with luteinizing hormone (in red). Luteinizing hormone (LH) spikes on ovulation day and in this example, BBT shows a marked increase 2 days afterwards.

*this photo is not mine but was taken from Google Images and premom.com

Working with a registered holistic nutritionist is a great way to learn more about natural family planning methods, ovulation, and your cycle in general. Knowing when and if ovulation is occurring is essential to fertility and pregnancy planning. You cannot get pregnant if you don’t ovulate and if you don’t know when you ovulate, it can take a lot longer to get pregnant. Optimizing time of intercourse depending on your unique cycle will be extremely beneficial if trying to become pregnant. The added benefit of working with an R.H.N. during the preconception phase (ie. before pregnancy happens) is that you can work to identify and replenish potential deficits in vital nutrients that will support your body to become pregnant and your developing fetus when the time comes.

One of the most crucial periods of fetal development occurs before a woman even knows she is pregnant (in the first few weeks after fertilization). This is just one reason why preparing your body prior to pregnancy is ideal for the baby because it starts its development with optimal maternal nutrient stores. If this resonates with you and you are ready to get started on your journey to pregnancy and motherhood, please send me a message at sarah.sajnovic@gmail.com or check out my specialized programs on my website. I cannot wait to work with you!

Helpful Links (not sponsored or affiliated in any way with these brands)

Amazon Thermometer

Premom Ovulation Test Kit – free app download

Etsy BBT Fillable Chart

References

Steward K, & Raja A. Physiology, Ovulation And Basal Body Temperature. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546686/

“Basal Body Temperature for Natural Family Planning.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 10 Feb. 2023, http://www.mayoclinic.org/tests-procedures/basal-body-temperature/about/pac-20393026.