Progesterone is called a pregnancy hormone because it plays a critical role in preparing the uterus for implantation of a fertilized egg and maintaining a healthy pregnancy. It is essential for establishing and sustaining the gestation period.
Here's a breakdown of its key functions:
- Thickening the Uterine Lining (Endometrium): Progesterone stimulates the thickening and enrichment of the endometrium, the lining of the uterus. This creates a receptive environment for the fertilized egg (blastocyst) to implant. Without adequate progesterone, the uterine lining may not be sufficiently prepared, leading to implantation failure.
- Maintaining the Uterine Lining: After implantation, progesterone continues to support the endometrium, preventing its shedding (which would result in menstruation and loss of the pregnancy).
- Preventing Uterine Contractions: Progesterone helps relax the smooth muscle of the uterus, preventing contractions that could dislodge the developing embryo or fetus.
- Supporting Placental Development: Progesterone supports the development of the placenta, the organ that nourishes the growing fetus throughout pregnancy. The placenta also becomes a major source of progesterone after the first trimester.
- Preventing Further Ovulation: Progesterone inhibits the release of eggs from the ovaries during pregnancy, preventing additional pregnancies from occurring.
- Breast Tissue Preparation: Progesterone prepares the breast tissue for lactation, although significant milk production does not typically occur until after delivery.
In summary, progesterone's roles in preparing the uterus for implantation, maintaining the pregnancy, and supporting fetal development are why it's commonly referred to as a "pregnancy hormone." Its presence and proper levels are vital for a successful and healthy pregnancy.
