Expansion
Colostrum first, then transitional and mature milk
Expansion
Stages
- Lactogenesis I: from mid-pregnancy, the breast becomes capable of secretion, but high progesterone blocks it
- Lactogenesis II: at 2 to 4 days after delivery of the placenta, progesterone falls and copious milk production begins
- Lactogenesis III: maintenance, which is demand led
Composition
- Colostrum (days 1 to 4): low volume, high protein, rich in secretory IgA, lactoferrin, leucocytes and growth factors. Low in fat and lactose
- Mature milk: higher in lactose and fat, lower in protein
- Foremilk is watery and hindmilk fat rich, which is why complete emptying of one breast matters
Advantages: passive immunity, reduced infection and necrotising enterocolitis, reduced allergy and later obesity, maternal benefits including reduced breast and ovarian cancer.
Deficient in: vitamin K (hence intramuscular vitamin K at birth to prevent haemorrhagic disease) and vitamin D (hence supplementation). Iron content is low but highly bioavailable, and stores last about 4 to 6 months, which is one reason for introducing solids at that age.