The presence of corpus luteum after ovulation indicates normal ovulation of the ovary. Generally after ovulation, as the pressure in the follicular cavity decreases, the follicular granulosa cells and endometrial cells of the follicle will invade into the follicular cavity, and then the corpus luteum will be formed. The corpus luteum secretes progesterone, which plays an important role in regulating menstruation and maintaining pregnancy. The formation of corpus luteum after ovulation indicates that the follicle is well developed and there is no obstacle to ovulation in the ovary. Because if the follicle is not well developed, the ovary will not ovulate, and of course there will be no corpus luteum formation. If there is an ovulation disorder in the ovary, the mature follicle may not ovulate and directly form a luteinized cyst, and certainly no corpus luteum will form. If pregnancy occurs after ovulation, the corpus luteum forms the corpus luteum gestationis, which is capable of secreting progesterone and maintaining the pregnancy, and usually atrophies after the third trimester. If there is no pregnancy, the ovarian corpus luteum will atrophy on its own before menstruation.