In plain words
Secretory activation is the name for the switch from to full milk. Mothers usually notice it as the . It is the same process as lactogenesis II. It usually starts around days 2 to 4 after birth, after the placenta is delivered and progesterone falls. The breasts feel fuller, warmer, and sometimes heavier, though some mothers notice little change. Milk production starts whether or not the baby feeds, but how often the breast is emptied in these first days shapes supply afterward. A delay can follow a long labor, a , diabetes, or significant blood loss. Mothers may hear about this stage in the hospital or in a feeding class.
The deeper version
Secretory activation is the endocrine from colostrogenesis to mature lactation, also called lactogenesis stage II. It follows withdrawal of progesterone after placental delivery, in the presence of , insulin, and cortisol, which closes between alveolar cells and drives synthesis of lactose, casein, and alpha-lactalbumin. Clinically it is recognized by maternal perception of breast fullness and by rising milk volume and lactose with falling sodium and protein. Delayed onset beyond 72 hours is reported in a substantial minority of first-time mothers (Dewey et al., 2003) and is associated with early and shorter breastfeeding duration. Neville and Morton (2001) give the most detailed account of the physiology.
Where it comes up
- When your milk comes inFeeding Your Baby
- Colostrum and the first days before milk comes inFeeding Your Baby
- How breastfeeding works: supply and demandFeeding Your Baby
- Engorgement when milk comes inPostpartum: Your Body
- Low milk supply: real, perceived, and what helpsFeeding Your Baby
What mothers here say about secretory activation
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Sources
- Dewey KG et al. — Risk factors for suboptimal infant breastfeeding behavior, delayed onset of lactation, and excess neonatal weight loss. Pediatrics 2003
- Neville MC, Morton J — Physiology and endocrine changes underlying human lactogenesis II. Journal of Nutrition 2001