There is a mid-cycle shift in the basal body temperature (BBT) after ovulation in women. This is caused by:
a. Biphasic changes in basal body temperature are characteristic of the ovulatory cycle and are mediated by alterations in progesterone levels.
b. An increase in basal body temperature by 0.3 to 0.5°C begins after ovulation, persists during the luteal phase, and returns to the normal baseline (36.2 to 36.4 °C) after the onset of the subsequent menstruation.