How do estrogen and progesterone secreted by the placenta support pregnancy once it has formed?

Sourav PanNovember 9, 2024

Answered step-by-step

The hormones estrogen and progesterone, secreted by the placenta during pregnancy, play crucial roles in supporting the pregnancy and ensuring a healthy environment for fetal development. Here’s how each hormone contributes to the maintenance of pregnancy:

1. Progesterone

• Maintenance of the Uterine Lining:
  • Progesterone is essential for maintaining the endometrial lining of the uterus. After fertilization, it prevents the breakdown of this lining, which is critical for supporting the implanted embryo. By maintaining a thick and nutrient-rich endometrium, progesterone ensures that the embryo has a suitable environment for growth and development.
• Inhibition of Uterine Contractions:
  • Progesterone reduces the contractility of the myometrium (the muscular layer of the uterus). This inhibition is vital to prevent premature contractions that could lead to miscarriage or preterm labor. It achieves this by downregulating oxytocin receptors and other factors that promote uterine contractions .
• Immune Modulation:
  • Progesterone plays a role in modulating the maternal immune response to protect the developing fetus from being recognized as a foreign body. This immune tolerance is crucial for the successful continuation of pregnancy .
• Preparation for Lactation:
  • While progesterone primarily supports pregnancy, it also prepares the breasts for lactation by influencing mammary gland development, although this role becomes more pronounced with other hormones later in pregnancy .

2. Estrogen

• Uterine Growth and Blood Flow:
  • Estrogen stimulates growth and vascularization of the uterine tissue, increasing blood flow to support the developing fetus. It enhances angiogenesis (the formation of new blood vessels) in the uterus, ensuring that there is an adequate supply of oxygen and nutrients. This increased blood flow is critical as it helps meet both maternal and fetal metabolic demands.
• Preparation for Labor:
  • As pregnancy progresses, estrogen levels rise significantly, which prepares the body for labor. It promotes changes in the cervix (cervical ripening) and enhances uterine sensitivity to oxytocin, which is important for initiating contractions during labor .
• Support for Fetal Development:
  • Estrogen is involved in various aspects of fetal development, including organ maturation and growth. It influences fetal adrenal function and plays a role in regulating other hormones necessary for development .
• Coordination with Other Hormones:
  • Estrogen works synergistically with progesterone and other hormones like human placental lactogen (hPL) to ensure that maternal metabolism shifts appropriately to support fetal growth. For example, it helps increase maternal insulin sensitivity and glucose availability for the fetus