Women only have 1 egg expelled each month, and women have about 300,000-400,000 primordial follicles when they reach puberty. Only one of these follicles can develop into a dominant follicle, that is, one that can grow to 18mm or more. The rest of the follicles develop to a certain level and degenerate on their own through the apoptotic mechanism. Only 400-500 follicles develop and ovulate in a woman’s lifetime. Normal women ovulate alternately on both sides of the ovary, but some ovulate continuously on one side.