It contains higher amounts of white blood cells and antibodies than mature milk, and is especially high in immunoglobulin A (Ig A), which coats the lining of the baby's immature intestines, and helps to prevent pathogens from invading the baby's system. The hormonal endocrine control system drives milk production during pregnancy and the first few days after the birth.
When the milk supply is more firmly established, autocrine (or local) control system begins.
When the breast is stimulated, prolactin levels in the blood rise, peak in about 45 minutes, and return to the pre-breastfeeding state about three hours later.
The release of prolactin triggers the cells in the alveoli to make milk. Some research indicates that prolactin in milk is greater at times of higher milk production, and lower when breasts are fuller, and that the highest levels tend to occur between 2 a.m. Other hormones—notably insulin, thyroxine, and cortisol—are also involved, but their roles are not yet well understood.
During this stage, the more that milk is removed from the breasts, the more the breast will produce milk.
This is the mechanism by which milk is transported from the breast alveoli to the nipple.
Even thinking about breastfeeding can stimulate this reflex, causing unwanted leakage, or both breasts may give out milk when an infant is feeding from one breast.
However, this and other problems often settle after two weeks of feeding.These include feeding in a familiar and comfortable location, massage of the breast or back, or warming the breast with a cloth or shower.Suckling by the baby innervates slowly-adapting mechanoreceptors that are densely packed around the areolar region.A poor milk ejection reflex can be due to sore or cracked nipples, separation from the infant, a history of breast surgery, or tissue damage from prior breast trauma.If a mother has trouble breastfeeding, different methods of assisting the milk ejection reflex may help.In humans the process of feeding milk is also called breastfeeding or nursing.In most species, milk comes out of the mother's nipples; however, the monotremes, egg-laying mammals, lack nipples and release milk through ducts in the abdomen.The increased pressure causes milk to flow through the duct system and be released through the nipple. The milk ejection reflex (also called let-down reflex) is not always consistent, especially at first.Once a woman is conditioned to nursing, let-down can be triggered by a variety of stimuli, including the sound of any baby.At birth, prolactin levels remain high, while the delivery of the placenta results in a sudden drop in progesterone, estrogen, and HPL levels.This abrupt withdrawal of progesterone in the presence of high prolactin levels stimulates the copious milk production of Secretory Activation.