During the luteal phase, when the body temperature can be around 37℃ and the high temperature state lasts for more than 15 days, the possibility of pregnancy is very high. Because the corpus luteum forms after ovulation, the body temperature center, stimulated by the corpus luteum, will cause the body temperature to rise, usually above 36.8℃. If there is no fertilized egg implantation, the corpus luteum will gradually atrophy, the body temperature will be about 13 days after ovulation, there will be a low temperature state, there is a low temperature for about 24 hours, will come to menstruation. After the fertilized egg is deposited, the body will secrete estrogen and progesterone, and the high temperature will continue.