What are the normal values for an endometrial biopsy?

The endometrium is the lining of the uterus, that is, the mucous layer that covers it. Throughout the menstrual cycle, this layer undergoes changes depending on the levels of hormones, such as progesterone and estrogens. At the beginning of the cycle (the first day of menstrual bleeding), the concentration of these hormones is reduced, causing the endometrium to shed with menstruation. 

Subsequently, the uterine lining thickens again to 10-16 mm with a trilaminar appearance and becomes receptive, which increases the chances of embryo implantation. If there is no conception, that is, if the egg is not fertilized, the endometrium is shed again and the menstrual cycle begins again.