Menstruation is the periodic exfoliation of the endometrium as well as bleeding that accompanies the change of the ovarian cycle in women. Some blood clots and flesh-like appearance of the uterus during menstruation first exclude pregnancy miscarriage, if except for pregnancy flow, these blood clots of flesh-like appearance are usually exfoliated endometrial tissues and do not need to be worried or to seek medical attention. As long as you are at childbearing age you are preparing for childbirth and if you do not conceive a child, the endometrium will be exfoliated. When the endometrial lining is exfoliated, there will be something membranous or even fleshy inside the menstrual blood, some patients will have membranous and some patients will have complete endometrial exfoliation, like flesh.