Basal body temperature refers to the body temperature when the body is awake and very quiet, not affected by muscle activity, mental tension, food and environmental temperature. After ovulation, the remaining part of the original follicle forms the corpus luteum, which produces a large amount of progesterone. Progesterone can stimulate the hypothalamic thermoregulatory center, which can increase the basal body temperature by 0.3~0.5℃ after ovulation, which can be used clinically as one of the signs to determine the ovulation date. Preparation for basal body temperature measurement: 1. a thermometer. It can be an ordinary mercury thermometer, or a high-tech electronic thermometer, or a special basal thermometer. 2, if the ordinary mercury thermometer, the thermometer before going to bed will be dumped to 35 ℃ or less; 3, before going to bed will be placed on the thermometer to wake up to reach the place, but can not be placed too close, so as not to sleep and turn over can not be pressed to the thermometer, resulting in its fracture to hurt themselves; 4, a basic body temperature measurement table, a pen. Third, the basic body temperature measurement precautions: 1, at least 6 hours of adequate sleep; 2, every morning after waking up, immediately measure the temperature, strictly forbidden to get up, walking, urinating and defecating, eating, talking, etc.; 3, because the axillary temperature is not as stable as the oral temperature, so it is recommended that the thermometer under the tongue to measure the basic body temperature, 5 minutes after taking out the reading; 4, timely record the results on the basic body temperature record sheet; 5, pay attention to record special events, such as the flu, a pen. 5, pay attention to record special events, such as colds, fever, alcohol, medication, late sleep, including intercourse, menstruation need to be marked; 6, the measurement time range should be measured within 5 days of the onset of menstruation, until the next menstruation within 5 days after the onset of menstruation or more than 15 days of the menstrual cycle, can not only measure the mid-menstruation alone.