My name is Line and I'm pregnant! Thank you OvuSense - after five years of trying, it took just two cycles with OvuSense to get pregnant. 

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Read more about Line's OvuSense journey here, or read on to go to our blog.

You may be aware that Basal Body Temperature (BBT) is your temperature when you’re at complete rest and that there is something often referred to as the “BBT method” for fertility tracking. But how does BBT tracking work? And what BBT changes can you expect to see in early pregnancy?

BBT is often used as a cheap and easy means of tracking and predicting ovulation. This is because ovulation can be characterized by a temperature rise of at least 0.2 degrees, which stays elevated for the rest of the cycle. This is due to the fact that during ovulation a woman’s progesterone levels rise, leading to a rise in BBT. 

After ovulation and until your next period, progesterone levels remain high and so does your temperature. These temperature changes, if measured accurately, can help women chart their cycles, identify potential cases of ovulatory infertility, and can even indicate early pregnancy.

BBT and pregnancy

As mentioned, after ovulation a woman’s progesterone levels stay high and so does her BBT. This is until her period, when an unfertilized egg sheds with her uterine lining. Progesterone levels drop along with BBT. However, if an egg is fertilized (and the woman gets pregnant), this drop in progesterone and temperature does not occur. This process is important to understand when we are talking about BBT in early pregnancy.

Although you shouldn’t rely on BBT measurements to tell you if you’re pregnant or not (taking pregnancy tests will give you a reliable answer), your BBT chart may provide some indications that you are pregnant.

A missed period and long luteal phase

The luteal phase is the time between ovulation and your expected period. As the luteal phase does not vary so much for many women, the greater the number of days past your usual luteal length you still haven’t got your period, the higher the chance of pregnancy. If your luteal phase is longer than 20 days, it would be a good idea to use a pregnancy test!

How is BBT measured?

BBT must be measured every day, first thing in the morning. The importance of this for accurate results cannot be overstated! Any activity (even sitting up in bed or walking over to the other side of the room) can cause a rise in your body temperature, and impact the validity of your measurements. A thermometer with a good level of accuracy can be used. You can log your measurements in a chart or with various apps.

Can the BBT method be improved?

The length of each woman’s cycle from month to month is known to be highly variable. The critical limitation of BBT is the fact that BBT on its own tells you when you have already ovulated. However, this can be combined with cervical mucus observations to look for the start of the fertile time. 

Some women find the BBT method impractical and inconvenient, however, if you are trying to conceive it does offer you some valuable information on your menstrual cycle and fertile time.

If you would like to start using a cycle tracking method to improve your chances of conception or to gain a greater understanding of your cycle, it can be useful to use a device that has the benefits of convenience and accuracy such as OvuSense

To find out how OvuSense compares to other tracking methods, read on here.