What is progesterone? Progesterone is a hormone that is secreted by the ovary after ovulation. Progesterone mainly acts on the female reproductive system of the human body and plays a vital role in changes in the female cycle. The role of progesterone in the ovary is mainly to promote the implantation process of fertilized eggs in the uterus and to maintain the normal growth and development of the fetus during pregnancy. The importance of progesterone in the reproductive system Progesterone is one of the important hormones in the female body. It plays many important roles.