The female reproductive system is all the parts of a woman’s body that help you reproduce, or have babies. The ovaries are consisting of two small organs is the main part of the female reproductive system. Before puberty, it’s as if the ovaries are asleep. During puberty, they “wake up.” The ovaries start making more estrogen and other hormones, which cause body changes. One important body change is that these hormones cause menstruating cycles. Once a month, the ovaries release one egg (ovum). This is called ovulation. As the egg travels, estrogen makes the lining of the uterus (called the endometrium) thick with blood and fluid. This makes the uterus a good place for a baby to grow. A woman can get pregnant if she has sex with a male without birth control and his sperm joins the egg (called fertilization) on its way to the uterus.