What role does progesterone play in early pregnancy?

Progesterone plays a crucial role in early pregnancy by maintaining the uterine lining. After conception, progesterone is produced primarily by the corpus luteum and later by the placenta. Its primary function is to prepare the endometrium for implantation of the fertilized egg and to maintain it throughout the first trimester, ensuring that the environment is suitable for the developing embryo. This hormonal support helps to prevent the uterine muscles from contracting, which could lead to the loss of the pregnancy.

In contrast, the other options do not accurately represent the key functions of progesterone in early pregnancy. While the hormone does influence various bodily functions, the stimulation of contractions occurs due to other hormones and is not a role of progesterone. Additionally, progesterone does not prevent ovulation after implantation of the fertilized egg, nor does it have a direct role in increasing milk production during early pregnancy. Instead, other hormones like prolactin are primarily responsible for that process.