When a woman becomes pregnant, levels of progesterone, prolactin and placental lactogen rise. The internal mammary tissue undergoes a remarkable expansion. This begins stage one lactogenesis.
During the latter part of pregnancy, the breasts are making colostrum, but high levels of progesterone keep the breast from making milk and keep the amount low. Around the time of birth, the circulating progesterone begins to drop.
At birth, the delivery of the placenta results in a quick drop in progesterone levels and stage two lactogenesis or milk secretion begins.
This abrupt withdrawal of progesterone in the presence of high prolactin levels cues lactogenesis II (copious milk production).
Although lactogenesis II begins approximately 30-40 hours after birth, mothers do not typically start feeling increased breast fullness (the sensation of milk coming in) until 50-73 hours (2-3 days) after birth.
These two stages of lactation are hormonally driven – they occur whether a mother is breastfeeding her baby or not.
Includes presence of ductal sprouting, mammary cell and lobular proliferation
Secretory Differentiation (Lactogenesis I)
Occurs about the 16th prenatal week
Initiation of milk synthesis
Differentiation of alveolar cells into secretory cells
Prolactin stimulates mammary cells to produce milk
Secretory Activation (Lactogenesis II)
Occurs after birth and delivery of placenta
Stage is triggered by rapid drop in mother's progesterone levels, increasing prolactin levels
Onset of copious milk secretion
Oxytocin Reflex (Milk Ejection Reflex)
Hormonal feedback achieved through direct stimulation of nerves in the nipple and areola with suckling controlled by the hormone oxytocin.
Mother’s report signs that the milk ejection reflex is active
A tingling sensation in the breast.
Leaking when it is time to feed the baby or when she is reminded of her baby.
One breast is leaking while she is nursing on the other.
If she removes the baby from the breast mid-feed, she may have sprays of milk.
Uterine contractions and pain in early postpartum.
Increased need for fluids while nursing.
Hormonal feedback achieved through direct stimulation of nipple and areola with suckling.
Galactopoiesis (Lactogenesis III)
This is the maintenance phase of milk production. Switch from endocrine to autocrine control.
Occurs from day 9 to beginning of involution
Stage of mature milk production
Controlled by Feedback Inhibitor of Lactation and Prolactin Receptor Theory.
Feedback Inhibitor of Lactation (FIL)- whey protein that moderates milk synthesis.
Concept of “supply and demand.”
Based on fullness of breast.
Synthesis slows when breastmilk accumulates (increased presence of FIL in milk)
Prolactin Receptor Theory
Prolactin and its subsequent receptor sites are required in the regulation of milk synthesis. When mom nurses frequently in the first 3 weeks, she makes more prolactin receptors on the lactocytes (milk-making cells).
When a mom has more receptors, her lactation hormones help her body make as much milk as her baby needs.
Formula supplementation in the early days and weeks, specifically when non-medically indicated, can disrupt feeding frequency and impact breastmilk supply if mom does not remove the milk with a pump.
Involution (Apoptosis of secretory cells)
Involution occurs in two stages, first the milk-making cells die and then are replaced by adipocytes. Milk stasis triggers involution. Predisposing factors for milk stasis include weaning, poor milk removal, scheduled feedings, some medications and engorgement.
Occurs typically 40 days after last breastfeeding.
Decreased milk secretion from buildup of inhibiting peptides.
High sodium levels are found in the milk of weaning mothers. They have also been found in the mothers of infants with failure-to-thrive, dehydration, malnutrition and hypernatremia when associated with low milk supply.
Clinical Guidelines
Kellams, A., Harrel, C., Omage, S., Gregory, C., & Rosen-Carole, C. (2017). ABM Clinical Protocol #3: Supplementary Feedings in the Healthy Term Breastfed Neonate, Revised 2017. Breastfeeding Medicine, 12, 188–198.
References
Campbell, S. H., Lauwers, J., Mannel, R., & Spencer, B. (2019). Core curriculum for interdisciplinary lactation care. Jones & Bartlett Learning.
Hale, T. W., & Hartmann, P. E. (2007). Textbook of Human Lactation. Hale Publishing.
Lawrence, R. A., & Lawrence, R. M. (2016). Breastfeeding: A guide for the medical profession (8th ed.). Elsevier.
Walker, M. (2017). Breastfeeding management for the clinician: Using the evidence. Jones & Bartlett Learning.
Wambach, K., & Riordan, J. (2016). Breastfeeding and human Lactation (5th ed.). Jones & Bartlett Learning.
