How do progestins regulate events during pregnancy?

Progestins, which include progesterone and synthetic steroid hormones with similar properties, are essential for the maintenance of pregnancy (pro-gestation).12

During pregnancy, progestins regulate several critical events:

• Uterine Preparation: Progesterone prepares the endometrium (uterine lining) to accept and support the implantation of a fertilized egg.12
• Uterine Stability: They inhibit muscular contractions of the uterus that could otherwise lead to the rejection of the implanted egg.1
• Hormonal Feedback: Once the placenta is formed, it becomes the primary source of progesterone. High levels of this hormone suppress ovulation, effectively preventing a second conception during the pregnancy.12
• Mammary Development: Progesterone stimulates the development of glands within the breasts, preparing them for future milk production.1

Without adequate levels of these hormones, a pregnancy would typically terminate.2