Lactation and Colostrum

Lactation is the production of milk by the mammary glands, glands that already respond to and change across every menstrual cycle and develop further throughout pregnancy itself. As pregnancy approaches its end, rising levels of oestrogen, progesterone and human Placental Lactogen stimulate the hypothalamus to release prolactin-releasing factors; in response, the anterior pituitary secretes prolactin, the hormone most directly responsible for driving milk synthesis, a process called lactogenesis. Once the baby begins suckling, a second hormone, oxytocin, triggers the so-called 'let-down' reflex — the actual mechanical ejection of milk that has already been made in the alveoli, pushing it out through the ducts to the nipple; as a further, separate effect during lactation, oxytocin also causes the recently emptied uterus to contract, helping it gradually return to its pre-pregnancy size. In the first few days after birth, before regular milk supply is established, the mammary glands secrete a distinct yellowish fluid called colostrum. Colostrum contains less lactose and almost no fat compared with mature milk, but is much richer in protein, vitamin A and minerals, and it carries immune, growth and tissue-repair factors — notably IgA antibodies, which specifically protect the newborn's digestive tract against bacterial infection. B …