The immature eggs are not automatically expelled, this is an invalid ovulation, generally belongs to the case of anovulation, the ovaries expel eggs, the necessary conditions for ovulation are as follows: a. The follicles must be developed and mature, the standard for mature follicles is judged from the size of the follicles, about 18-22mm is called mature follicles. If the follicle is less than 18mm, it cannot be expelled and will shrink and degenerate on its own under certain apoptotic mechanisms. If more than 22mm mature follicles are not yet expelled, it is an ovulation disorder. Follicle maturation is the first condition for ovulation, but it does not mean that mature follicles will definitely be expelled. Secondly, there must be a peak of LH luteinizing hormone, which is a hormone secreted by the pituitary gland. Therefore, some women cannot ovulate even when their follicles are mature, probably because the luteinizing hormone in the body has not reached its peak value and the value is too low. Follicular maturation must also require the release of proteolytic enzymes from the follicular wall, thus dissolving the follicular wall, for the follicle to be able to expel the egg. If the follicular wall is too thick, the follicle in the ovary may not be able to expel the egg either.