Physiology of Breast Milk Production

Physiology of Breast Milk Production

Regardless of the mother’s physical condition, method of delivery (Cesarean section or vaginal delivery) or breast size, milk will be produced. Increase levels of estrogen and progesterone during pregnancy suppresses lactation as increase in the level of these hormones inhibits prolactin production. However, increase levels of these hormones early in pregnancy stimulate the growth of milk glands in preparation for lactation. This is the main reason why pregnant women’s breasts tend to increase in size due to larger glands that result to more fluid accumulation and formation of some extra adipose tissue.

Estrogen and progesterone levels drop after delivery that stimulates the production of prolactin. Prolactin is responsible for breast milk production. If the mother wants to suppress lactation, lactation suppressing agents should be given immediately after placental delivery to be effective. The milk ducts become distended when breast milk begins to form. The woman’s breasts become fuller, larger and firmer. For some this is accompanied by a throbbing pain or feeling of heat in the breasts. The feeling of tension in the breast that most likely occurs by the third or fourth pospartal day is called engorgement. Relief is achieved when the neonate starts to effectively suck the breasts or for those who have no plans of breastfeeding using a breast pump would be provide immediate alleviation.

The infant has to effectively suck the milk for relief to occur. Effective sucking means the infant is actually receiving milk. A baby can suck the breast without actually swallowing milk but rather swallowing air. One criteria of knowing that effective sucking is done by the baby is when the mother hears a soft “ka” or “ah” sound during feeding. This indicates that the infant is swallowing the colostrum or milk.

Let-down reflex is the one responsible for pushing the milk outside the breast. This reflex is stimulated by the release of oxytocin. Oxytocin on the other hand, is released when an infant sucks the breast or the mother uses a breast pump.

The following sequential pattern occurs during breast milk production:

  1. Levels of estrogen and progesterone drops after the delivery of the baby.
  2. Decreasing amounts of these hormones stimulates the anterior pituitary glands (APG) to produce prolactin.
  3. Prolactin stimulates the foremilk production in the glandular tissues of the breasts.
  4. Foremilk is stored in the collecting tubules of the breasts, ready for infant feeding.
  5. When the infant sucks the breast or a breast pump is used by a woman, the posterior pituitary gland (PPG) is stimulated to produce oxytocin.
  6. Oxytocin causes contraction of the smooth muscles or the collecting tubules. (this is the reason why afterpains are felt by women who breast feed their babies)
  7. 7. Contraction causes the ejection of the milk forward and outside the breasts – Let-down or Milk Ejection Reflex.
  8. Hindmilk is produced.

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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