The two hormones that are vital to the female reproductive system are estrogen and progesterone. These two hormones are secreted by the ovaries.
Estrogen is the "female hormone" and regulates the appearance of secondary sex characteristics during puberty, such as breast development, increasing body fat, pelvic widening, and body hair. After full maturity, estrogen regulates the health of female reproductive organs such as the uterus, and regulates menses during the normal reproductive lifespan.
Progesterone is the "pregnancy hormone" and is responsible for many functions, including the preparation of the uterus and lactation glands for pregnancy. It is also involved with menstruation, increasing in preparation for pregnancy and then decreasing rapidly as menstruation occurs.
Both of these hormones are vital to the health of the female reproductive system, and a deficiency in one or both can cause harm to both the woman and to a developing fetus.