General normal menstruation to 28 days, about the 14th day is ovulation, the 20th day of menstruation should be after ovulation, there is brown discharge, probably these three cases: the first case, after ovulation may be due to fluctuations in hormone levels or follicular growth is poor, there will be hormonal fluctuations caused by a small amount of endothelium after the endothelium to produce a brown secretion; the second case, it may be in the ovulation, some patients ovulation relatively In the second case, it may be before ovulation, some patients ovulate late, so by the 20th day there is no follicular growth, not yet able to ovulate, there is no progesterone to counteract the effect of estrogen fluctuations caused by a small amount of endothelial shedding and bleeding; in the third case, there are also patients with slower growth of follicles, almost to about 20 days before ovulation, in the ovulation due to the hormone fluctuations there will be a small amount of bleeding.