What is Basal Body Temperature tracking and why is it so important for cycle health?
Basal body temperature (BBT) tracking is a method used to track your cycle and monitor ovulation by taking your temperature every morning before getting out of bed. This method involves measuring the body's resting temperature. which is the lowest temperature reached by the body during sleep.
BBT tracking is performed using a thermometer that is accurate to one tenth of a degree (0.01). If taking your temperature at the exact same time every morning is difficult, there are a range of wearable thermometers that calculate your average temperature for the night such as the Oura ring (https://ouraring.com/) and TempDrop (https://tempdrop.refr.cc/ellenfreeman). If using an oral thermometer, most cycle tracking apps will have a section for BBT input, but my favourites to use are Natural Cycles (https://www.naturalcycles.com/) or Fertility Friend (https://www.fertilityfriend.com/). When using an oral thermometer, your temperature must be taken FIRST THING in the morning, before getting out of bed. My favourite tip for remembering to do this is to place your thermometer on your phone- as this is typically the first thing we all reach for first thing!
How does my BBT reflect ovulation?
During the first half of the menstrual cycle. the hormone oestrogen is dominant, which causes the follicles in the ovaries to grow and mature. As the follicle matures, it produces more oestrogen, which causes the cervix to produce fertile cervical mucus and prepares the uterus for implantation.
When ovulation occurs, the mature follicle releases an egg. which is then fertilized by sperm or is shed during menstruation. After ovulation, the ruptured follicle forms a structure called the corpus luteum, which produces progesterone. Progesterone is responsible for raising the BBT and maintaining the lining of the uterus in preparation for implantation. If pregnancy does not occur, the corpus luteum stops producing progesterone, and the BBT returns to its lower pre-ovulatory level, leading to the start of a new menstrual cycle.
Why should I track my BBT?
BBT tracking provides important insights into your menstrual cycle health. By monitoring the changes in basal body temperature over several cycles, you can gain a better understanding of your cycle and identify any potential issues that may need attention.
BBT tracking can also be used as a method of contraception (also called the Symptothermal method), or as a method of timing intercourse for conception. Knowing whether you’re ovulating (if not on any form of contraception) is an incredibly powerful tool to monitor your overall health.
Ways that tracking BBT assists with cycle health
Identifying luteal phase defects: The length of the luteal phase, which is the time between ovulation and the start of the next period, can be determined through BBT tracking. A luteal phase that is consistently shorter than 10 days may indicate a luteal phase defect, which can affect fertility.
Monitoring fertility treatments: BBT tracking can be useful for monitoring the effectiveness of fertility treatments such as ovulation induction or in vitro fertilization (IVF).
Confirming ovulation: BBT tracking can help confirm whether ovulation has occurred, and if so, when it occurred. This can be helpful for women who are trying to conceive or those who have irregular cycles.
Detecting hormonal imbalances: Abnormalities in BBT patterns can indicate hormonal imbalances, such as thyroid dysfunction or polycystic ovary syndrome (PCOS).
Why is tracking your BBT over a full cycle important?
An increase in temperature following ovulation is important as it shows a ‘biphasic’ cycle (meaning having two phases). The first phase of your cycle is the Follicular phase, temperatures are typically around 36.2-36.4 degrees celsius. Following ovulation, the second phase of the cycle is the Luteal phase, these temperatures should be higher than the first phase and are usually around 36.7-37 degrees. Charting your temperature for your entire cycle is important to accurately show when ovulation occurs, and for the length of each phase of your cycle.
What if I’m a shift worker/new parent/have difficulty sleeping?
Your temperature should be taken after a minimum of 4 hours sleep. If this is difficult to achieve using an oral thermometer, I’d highly recommend using a wearable thermometer such as the Oura ring or Tempdrop, for their ability to take an average of your temperature throughout the night. If getting a consistent amount of sleep does prove difficult, your BBT chart may look slightly more erratic with temperatures going up and down- though a clear bi-phasic chart should still be visible.
Other factors that will influence your BBT chart include illness, alcohol and high amounts of stress.
What are my best tips for starting out with BBT charting?
Work with a professional! Working with a trained fertility acupuncturist is a great asset to help understand the in’s and out’s of charting while you’re learning the ropes
Find a method that works for you- whether it’s using an oral thermometer or a wearable thermometer, choose a method that resonates with you and that you think will best suit your needs and lifestyle
Read up on resources- I’ve included below some of my favourite socials and practitioners that I referred to a lot when I was first learning about BBT charting.
My favourite BBT socials and resources
@fertilitycharting - Great info source for all things BBT tracking
@fertilityawarenessproject - Certified fertility awareness educator
@larabriden - Women's health MD
@jenna_thefertilitysuite - Easy to understand information on all things fertility
@tempdrop – Excellent blog posts and resources for understanding BBT charting
Do you need some help deciphering your BBT chart, are looking to fall pregnant or regulate your cycle? I’m here to help! You can find me in Greenslopes, QLD @ Womb to World and Everton Hills, QLD @ Pack Health. Book via the ‘Book Now’ tab on my website. I look forward to meeting you. - Dr Ellen Freeman (TCM)
