I briefly discussed Basal Body Temperature charting in last weeks post on ovulation. I noted how it is a useful tool that can help you track ovulation. If you know you are ovulating and when, this can help you to get the timing right for conception.
Basal Body Temperature (BBT) is your body’s resting temperature, during our menstrual cycle there is a slight variation in our BBT as the hormones oestrogen and progesterone fluctuate. In the first phase of our cycle, the follicular phase, oestrogen is dominant and your BBT will be around 36 degrees Celsius. When ovulation occurs there may be a slight dip in your BBT and as progesterone rises in the luteal phase your BBT will also rise. BBT should remain at this higher level for the remainder of your cycle until you have your period (it will remain raised if pregnant).
Basal Body Temperature charting
The example of Basal Body Temperature charting above depicts a biphasic chart. Temperatures are between 36.2 and 36.3 during the follicular phase. There is a slight dip down to 36.1 when ovulation occurs and the temperature rises up to 36.5 and above in the luteal stage. The difference in BBT is minor but you can see the 2 distinct temperature ranges.
If your chart is not biphasic or if it takes a few days for the rise in temperature to occur you may not have ovulated. No matter what your chart looks like it will be useful for your practitioner to review to identify what might be going on and if needed investigate further.
When you do basal body temperature charting for a few cycles you will have a good idea when in your cycle you are ovulating. Once you know this it allows you to better plan for conception. An egg only survives 12-24 hours after ovulation so you need to time intercourse for the sperm to be present and waiting for the egg as it travels to the uterus. Ideally aim to have intercourse every second day starting a few days prior to expected ovulation. If you refer back to the example above, the circles indicate days when intercourse is recommended.
3 simples steps to complete Basal Body Temperature charting
Step 1. You will need to purchase a BBT thermometer, this thermometer measures very minor temperature changes to 2 decimal places. Purchase one that goes under the tongue for ease of use.
Step 2. You need to take your temperature as soon as you wake up every morning, remember we are measuring your resting body temperature so it needs to be taken before you get out of bed, talk to anyone, drink anything or move around. Place the thermometer next to your bed where you can access it easily without needing to get out of bed.
Step 3. Put the thermometer on the same side of your mouth everyday, wait for the beep, note down your temperature to the decimal point and plot it on a paper chart or in an app.
BBT can be impacted by, less than 3 hours sleep, poor quality and frequently interrupted sleep, high stress, the use of an electric blanket, having a fever due to illness and alcohol, drug or medication use. Note down any factors that may have influenced a daily reading so that you can look back at the end of your cycle and understand what might have been happening.
If you would like more information on Basal Body Temperature charting, to talk through how to get started or if you have been charting your BBT and need help deciphering the chart please get in touch with us here at Sydney Natural Fertility and we can help.
References:
Steward, K., & Raja, A (2023). Physiology, Ovulation and Basal Body Temperature. In Stat Pearls Internet link to article below.
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