The brown discharge two or three days before menstruation may be implantation bleeding, but it is not absolute, it may also be caused by insufficient estrogen secretion in the body. Sexual intercourse before the onset of menstruation, sperm and egg to form a fertilized egg, two or three days before menstruation brown discharge may be fertilized egg implantation bleeding, fertilized egg in the process of invasion, the trophoblast cells of the fertilized egg penetration invasion of the uterine endometrium, myometrium, blood vessels, and ultimately completely buried in the endometrium of the process, it will be stimulated to the peripheral blood vessels resulting in a small amount of vaginal bleeding. Two or three days before menstruation brown discharge may also be insufficient secretion of progesterone in the body, there is a small amount of endometrial stripping caused by bleeding, the amount of blood is relatively small, in the uterus stagnation for a period of time to be oxidized, and mixed with the leukorrhea discharged is the brown discharge. If the bleeding before menstruation is caused by implantation, menstruation will be suspended after successful implantation, and you can also find out whether a woman is pregnant by taking an early pregnancy test.