The length of the menstrual cycle varies from person to person and should normally be within the range of 28±7 days, of which the pre-ovulatory day is called the follicular phase and the post-ovulatory day is called the luteal phase. The length of the follicular phase varies, but the normal post-ovulatory luteal phase is about 14±2 days. The day after ovulation, the ovaries form the corpus luteum, which secretes progesterone and estrogen, causing the basal body temperature to rise by about 0.4°C for 12-16 days, thus showing a biphasic change in the basal body temperature curve of the menstrual cycle, which is low before and high after. If there is no pregnancy, the corpus luteum gradually shrinks and stops producing progesterone, the basal body temperature drops and returns to the pre-ovulatory temperature level, and at the same time, menstruation comes. If pregnancy occurs during the month, the body temperature shows a continuous high temperature phase because the corpus luteum is supported by hormones secreted by the embryo and continues to secrete estrogen and progesterone. When there is ovarian malfunction, insufficient luteal production or incomplete atrophy, the rise in body temperature is not obvious and lasts for a shorter period of time. When the body temperature shows a continuous low temperature with no high or low changes, it indicates that the ovaries are not ovulating normally, or that the ovaries are low in function. Women who are ready to get pregnant should estimate the possible ovulation day of the month according to their menstrual cycle to seize the best time to conceive. Of course, nature is also amazing. A few days before ovulation day, because of the influence of estrogen, women will experience an increased sexual desire and naturally produce a lot of clear and odorless leucorrhea, which is the best time to have intercourse.