Every month, during the childbearing years, a woman's body prepares an egg for possible fertilization. A woman's entire supply of eggs actually develops when she is a fetus. A newborn girl has approximately 2 million immature eggs at birth. By the time puberty arrives, the number has been reduced to about 300,000 to 400,000 eggs. Each month the hypothalamus of the brain tells the pituitary gland to secrete follicle-stimulating hormone (FSH) which causes the ovaries to produce a mature egg. The egg matures within a small cavity in your ovary called a follicle. A few days later, when the egg is at the proper stage, the pituitary gland secretes the next hormone called lutenizing hormone (LH) which causes the follicle to swell and burst through the wall of your ovary, releasing the egg. This is called ovulation. You have two ovaries, but in any given cycle, ovulation occurs from just one of them. In the mean time, the hormones estrogen and ...