BBT

Body basal temperature (BBT) is the lowest temperature that your body reaches during each 24-hour day. This “resting” temperature is usually reached during deep sleep and then increases as you wake up.

Why BBT?

BBT is the oldest method of fertility monitoring and was first used in the 1930s. It is a well-established and trusted method of ovulation detection.

How Does BBT Change Throughout my Cycle?

Women’s BBT patterns are biphasic^? i.e. they consist of two different phases during the menstrual cycle. The temperatures taken in the phase before ovulation are lower than those taken in the phase after ovulation. The average temperature prior to ovulation is 36.37oC and after ovulation is 36.72oC although this varies from woman to woman and cycle to cycle. This small increase in BBT will occur within 48 hours of ovulation and will remain elevated until your next period.

Why Does my BBT Change?

During the first phase of your cycle, high levels of oestrogen in your body keep temperatures low. Your raised BBT after ovulation is due to the level of progesterone^? in your body. Progesterone is secreted by the corpus luteum^? (the empty egg^? sac that the egg emerges from) and indicates that you have ovulated. This is why measuring BBT is the only method that actually confirms that ovulation has occurred.

Current Methods of Measuring BBT

Traditional methods of recording your BBT involve taking an oral, rectal or vaginal measurement at the same time each morning. These measurements must be taken as soon as you wake as even the act of waking or getting out of bed will increase your temperature, leading to inaccuracies in your data. As a result, these methods tend to generate “noisy” data, which can be confusing when trying to identify such a small change in temperature. Therefore most of these methods abide by the 3 over 6 rule – ovulation can be confirmed if you see 3 high temperatures following 6 low temperatures. However, confirmation that you have ovulated 3 days after the event is too late to take action, as the egg only survives for up to 2 days!

How DuoFertility Revolutionises BBT Monitoring

Although BBT is a trusted method of ovulation detection, it can only confirm ovulation after the event. While DuoFertility relies mainly on BBT for its analysis, it also uses a number of other factors such as cervical mucus^? quality and mood, all of which are related to ovulation, in its analysis. This allows it to accurately predict when you are ovulating up to 6 days in advance, giving you plenty of time to plan intercourse for the best time of the month. Incorporating these factors increases the accuracy of detection of your fertile days to up to 99.7%. DuoFertility is currently the only fertility monitor on the market to incorporate these factors into its analysis.

Read more about cervical mucus

Read more about cervix position

Read more about other ovulation signs