What is the main role of progesterone during pregnancy?

Progesterone plays a critical role in maintaining pregnancy, primarily by ensuring that the uterine environment is suitable for a developing embryo. One of its most significant functions is to maintain the uterine lining, also known as the endometrium, which is essential for implantation of the embryo. After fertilization, progesterone levels rise to support the thickening and vascularization of the uterine lining, creating an optimal environment for the embryo to grow.

Additionally, progesterone helps to prevent premature contractions of the uterus during pregnancy. It does this by relaxing the smooth muscle of the uterus, which is crucial to prevent spontaneous abortion and ensure that the fetus can develop without interruption. This action is vital for maintaining a stable pregnancy until the fetus is mature enough for delivery.

While other hormones and processes support fetal growth, lactation, and blood supply, progesterone's primary emphasis during pregnancy is on nurturing and stabilizing the uterine environment for the embryo, preventing contractions, and supporting the necessary changes in the endometrium.