Basal Body Temperature Shift

The basal body temperature is the body’s baseline resting temperature. It is a measure of the heat produced by body metabolism. Metabolism is slower in the preovulatory phase of the cycle thus a woman’s body temperature is slightly cooler. After ovulation progesterone is produced. Progesterone speeds up the body’s metabolism in anticipation of pregnancy, which causes a woman’s body temperature to rise and remain higher until menstruation occurs, or if she were to become pregnant, until the end of pregnancy.

When basal body temperatures are plotted daily the shift to a higher temperature after ovulation is easily noticed.