What does progesterone do during pregnancy?

Progesterone plays a crucial role during pregnancy primarily by maintaining the uterine lining, which is essential for the implantation and sustenance of the fertilized egg. This hormone ensures that the endometrium remains thick and receptive, providing a supportive environment for the embryo. Additionally, progesterone relaxes the smooth muscle, contributing to the relaxation of the uterus and preventing contractions that could lead to premature labor. These functions help create an optimal environment for both fetal development and the overall progression of pregnancy.

While other functions, such as preventing ovulation and supporting fetal development, are important aspects of reproductive health, they are not the primary roles of progesterone during pregnancy. Milk production, for instance, is more directly affected by other hormones like prolactin. Thus, the emphasis on progesterone's role in maintaining the uterine lining and its muscle-relaxing properties is critical to understanding its importance in pregnancy.