What is basal body temperature: The body temperature measured when the body wakes up after a long sleep (6 hours) and before any activity is performed is called the basal body temperature. Principle of basal body temperature: The basal body temperature of normal women of childbearing age varies cyclically, as does the menstrual cycle, and this temperature change is related to ovulation. The length of the menstrual cycle varies from person to person, ranging from 21-35 days, with an average of about 28 days, separated by the day of ovulation, which is divided into the follicular phase before ovulation, and the luteal phase after ovulation. The length of the follicular phase varies, but the luteal phase is fixed at about 14 days and the next two days. On the day after ovulation, the luteal phase is formed by the ovaries, and the secretion of luteinizing hormone causes the body temperature to rise by about 0.6 degrees Celsius, resulting in high and low body temperature changes. The high temperature period lasts about 12-16 days (average 14 days). 1.If there is no pregnancy, the corpus luteum atrophies and stops secreting luteinizing hormone, the body temperature drops and returns to the basic line, and menstruation comes. 2.If you are already pregnant, because the corpus luteum is supported by the hormone secreted by the embryo, it continues to secrete luteinizing hormone and the body temperature continues to be high. 3.If the ovaries are not functioning well, there is no ovulation and no corpus luteum formation, the body temperature will continue to be low. How to measure and record basal body temperature? 1. Buy a basal thermometer. The basal thermometer is different from the general thermometer, it has a dense scale, generally 36.7 degrees Celsius (scale 24) as the dividing line between high and low temperatures. (36 degrees – scale 10; 38 degrees – scale 50). 2.Place the basal thermometer on the pillow where you can get it at hand before going to bed, and put it under your tongue for three minutes when you wake up the next day, before you get up and move around, and record it on the basal thermometer. 3.For those who have difficulty in measuring body temperature in the morning, you can measure it at a fixed time every day, remembering not to exercise vigorously or drink hot or cold food for half an hour beforehand. 4.The day of menstruation and intercourse should be marked with a mark. In case of fever, excessive drinking, late sleeping and late waking, etc., which may affect the body temperature, special notes should be made.