Natural FP - The temperature method
When your body is at rest, like in the morning when you wake up, it maintains a certain temperature called the basal temperature. When your ovary releases an egg, this temperature goes up a little bit. The basal temperature is recorded using a special kind of a thermometer, different from the one used to record temperature when you have a fever.
If you have sex two to three days before your temperature peaks and the day after that, you are likely to get pregnant. The chances of getting pregnant drop after the third day of a rise in basal temperature. You need to track and record your basal temperature. Your health care provider can show you how.
Attribution: Avallain