BBT Charting: How Reliable Are the Results?

I have just started to chart my basal body temperature. With so many factors affecting a person's temperature, how can this method be reliable?


Toni Weschler, MS

Toni Weschler is the author of the popular book Taking Charge of Your Fertility. By offering a simple and effective means of identifying... Read more

I really recommend fertility charting that includes the other two fertility signs -- cervical fluid and cervical position.

There are factors that can affect temperatures, but the trick is to learn how to see the forest through the trees and identify a pattern of lows and highs before and after ovulation, rather than focusing on any one particular temperature.

This is where the coverline is so critical. To draw the coverline, identify the first time your temperature rises at least 2/10ths higher than the highest of the last six days. Then draw the coverline a tenth of a degree above the highest. In a typical cycle, your temperature will remain above the coverline for about 12 to 16 days before you get your period. Whenever you have a temperature that seems out of line, you may be able to apply the rule of thumb, which says that you can choose to cover the outlying temperature with your thumb when you are drawing your coverline. Doing so will allow you to connect the lines without including the outlying temperature, making it easier for you to see the big picture.

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