Britannica Sources used in this answer

How does progesterone from the corpus luteum prepare the uterus for pregnancy?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

Following ovulation, the corpus luteum secretes progesterone, which plays a critical role in preparing the uterus for a potential pregnancy.21

Progesterone regulates the condition of the endometrium, the inner lining of the uterus, making it suitable for the implantation and development of a fertilized egg. Specifically, the hormone facilitates the following changes:21

Lining Preparation: It modifies the uterine wall to ensure it is receptive to the fertilized egg, supporting its attachment and subsequent nourishment of the embryo.21
Contraction Inhibition: It inhibits muscular contractions of the uterus that could otherwise cause the uterine wall to reject an adhering egg.1

If fertilization does not occur, progesterone levels drop after approximately 10–14 days, causing the uterine lining to stop growing and eventually break down, which leads to menstruation. If implantation is successful, the resulting placenta takes over the production of progesterone to maintain the pregnancy.21