Basal Temperature -

Sustained higher temperatures until the next period begins.

The accuracy of BBT tracking depends heavily on consistency. Because the margin of change is so small, various factors can "mask" the true basal reading. These include: basal temperature

The primary utility of tracking BBT lies in its relationship with the menstrual cycle. In the follicular phase (the first half of the cycle), estrogen keeps the BBT relatively low. However, immediately following ovulation, the corpus luteum begins producing . Progesterone has a thermogenic effect on the hypothalamus, causing the BBT to rise by roughly 0.5 to 1.0 degree Fahrenheit. This shift creates a "biphasic" pattern: Follicular Phase: Lower temperatures. Sustained higher temperatures until the next period begins