Basal Body Temperature Basics

The pros and cons and a brief how-to

In this article:
What Are the Benefits of Using BBT?
What about the Drawbacks?
How Successful Is BBT in Predicting Fertility?
Charting Your BBT: A Step-by-Step Guide
Some BBT FAQs

If you are trying to conceive a child, knowing when you ovulate is obviously helpful. Not every woman ovulates at the exact same point during her cycle, however, making any sort of standardized assumptions irrelevant. In order to know when you ovulate and when your best chances of conceiving are, you need a reliable fertility measurement system.

Now, it might seem strange the first time you hear of it, but there is a way to track your fertility throughout the month, without even getting out of bed. That method is BBT charting, named for the measurement you track: your basal body temperature (BBT).

What is BBT? The basal body temperature is your temperature immediately after you wake up in the morning, before you do anything. A woman's basal temperature changes in a regular pattern throughout her cycle, based on hormonal changes in her body. Tracking your temperature is a way of tracking your reproductive hormones, and thereby knowing just where you are in your cycle. That's it in a nutshell, really. However, the process of charting your BBT involves a bit more information, which we will get to shortly. It is important we look at some of the pros and cons of using BBT as a fertility metric before you decide to plunge right in.

What Are the Benefits of Using BBT?

The benefits of using BBT are numerous for figuring out when you are or will be most fertile. It is inexpensive, with basal thermometers being only a modest, one-time outlay. It is low impact, as the most invasive thing you have to do is put the thermometer in your mouth. It is low-mess—it only involves a small thermometer, some sheets of paper, and a pencil, which you can stow in your bedside table. (And, it gives you excellent justification for lying in bed just that one minute longer!)

But BBT tracking brings with it many other benefits as well, according to Dr. Angie Beltsos, OB/GYN, Medical Director of Fertility Centers of Illinois. BBT is a good way of showing when conception has occurred—your temperature stays elevated when it would otherwise drop. It can also help uncover certain fertility issues such as the luteal phase defect, which is when you appear to have a period between ovulation and menstruation. Its primary benefit for those seeking to conceive, however, is acting as a means of tracking the "consistency of ovulation," says Beltsos. Once you are familiar with your cycle, you will be much more aware of when is the right time to try. You will also simply know your body better through close observation, and that will help with both trying to conceive and maintaining your health in general.

Should you ever decide to see a fertility specialist, you will have a load of empirical evidence to share with her.