Medical Health Encyclopedia

Breast milk

The human breast does not store a large volume of milk, as cows do. Suckling stimulates the release of a hormone (prolactin) which stimulates milk production and the release of another hormone (oxytocin). Oxytocin, in turn, stimulates contraction (or the "let-down reflex") of the milk glands. The milk is squeezed out of the milk gland, into the milk ducts, and into the nipple.

At the beginning of the feeding, the milk is bluish and contains lactose and proteins, but little fat; it is called foremilk. The end of the feeding produces hindmilk. The hindmilk contains more fat, the main source of energy for your baby. If breast milk is allowed to sit for half-an-hour after being expressed, the "cream" separates and settles on top of the watery part. This is because human milk isn't homogenized, the process that makes the water and fat portion in milk stay blended.

MILK EJECTION REFLEX

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Some mothers feel a tingling sensation as the milk begins to eject from the breast due to the let-down reflex. The best way to monitor whether this milk-ejection reflex has begun is by watching the sucking and breathing patterns of your baby.

At the start of a feeding, you will notice a pattern: suck, suck, suck, swallow, suck, suck, suck, swallow. This pattern may last up to 30 seconds, but could be longer. As the milk ejection reflex takes over, the pattern may be described as gulping: one swallow, one deep breath, one swallow, one deep breath. This pattern may last for 2 - 4 minutes.

Your baby may want to nurse longer (maybe 15 or 20 minutes) on this breast in order to get more fat from the hindmilk or because your baby needs to fill a need for sucking. Rather than watching the clock to let him nurse 10 minutes on each side, you may want to allow your baby to pull away from the first breast naturally before switching to the other breast.

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