The hormones produced by the placenta and their functions are vital for supporting pregnancy, ensuring proper fetal development, and adapting the maternal body. As a temporary yet powerful endocrine organ, the placenta releases several hormones that regulate maternal physiology, support the fetus, and prepare the body for childbirth.

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Overview: Placenta as an Endocrine Organ

The placenta begins forming after fertilization and becomes fully functional by the end of the first trimester. Apart from its roles in nutrient exchange, waste removal, and oxygen transport, it also acts as a hormone-secreting organ that maintains and regulates pregnancy.

📘 Learn more: TeachMeAnatomy – Placenta


Major Hormones Produced by the Placenta

1. Human Chorionic Gonadotropin (hCG)

  • Detected in pregnancy tests within 6–8 days of fertilization
  • Maintains the corpus luteum in early pregnancy
  • Stimulates continued secretion of progesterone and estrogen
  • Helps prevent menstruation and supports implantation

🔍 Read more: American Pregnancy Association – hCG


2. Progesterone

  • Initially produced by the corpus luteum, but the placenta takes over around week 10
  • Maintains the uterine lining for implantation
  • Suppresses uterine contractions to prevent preterm labor
  • Supports breast tissue development for lactation

3. Estrogen (Primarily Estriol)

  • Increases uterine blood flow and growth
  • Stimulates breast development in preparation for lactation
  • Enhances the function of progesterone
  • Promotes cervical ripening late in pregnancy

🧠 Explore more at Visible Body – Pregnancy Hormones


4. Human Placental Lactogen (hPL or hCS)

  • Modifies maternal metabolism to ensure glucose availability for the fetus
  • Promotes lipolysis in the mother, providing energy from fat
  • Stimulates mammary gland development
  • Contributes to insulin resistance in the mother during late pregnancy

📚 More reading: Endocrine Society – hPL


5. Relaxin

  • Softens the cervix in preparation for childbirth
  • Relaxes the pelvic ligaments to accommodate labor
  • Works with progesterone to maintain uterine quiescence

6. Corticotropin-Releasing Hormone (CRH)

  • Regulates fetal adrenal gland activity
  • Promotes lung development by increasing surfactant production
  • Plays a role in timing of labor and parturition

Summary Table: Placental Hormones and Functions

Hormone Main Functions
hCG Maintains corpus luteum, prevents menstruation
Progesterone Supports endometrium, inhibits uterine contractions
Estrogen Promotes uterine growth, breast development
hPL/hCS Alters maternal metabolism, supports fetal nutrition
Relaxin Prepares pelvis and cervix for labor
CRH Stimulates fetal development, regulates labor timing

Conclusion

The hormones produced by the placenta and their functions are essential for ensuring a successful pregnancy. These hormones not only maintain the maternal environment but also directly influence fetal growth, maternal adaptation, and the timing of birth. Any imbalance in these hormones may lead to complications such as gestational diabetes, preterm labor, or placental insufficiency.

🔬 For more, visit National Institute of Child Health and Human Development (NICHD) – Placental Function