Charting temperatures helps a woman to know when she has ovulated, and possibly even if she is pregnant. It can also tell a woman if she has a problem, such as not ovulating - called anovulaion and low progesterone and thyroid dysfunction. This is due to the hormone estrogen. After ovulation occurs, the temperature has what is called a shift upward, usually about .4. This is indicating that the egg has been released, and usually by the time you see the temperature shift - the egg has either been fertilized or has died.
Progesterone is the hormone released after the egg has moved into the fallopian tubes.
The higher temps will stay this way for the length of the luteal phase - the time from ovulation to menstruation. This will vary from woman to woman. Usually it averages around 12 to 14 days. In order to effectively chart your temperatures, you need to have a good basal body thermometer. A fever thermometer is not good to use, because it won t tell the temperature to the .1 degree like a basal body thermometer will.