The 'let-down' reflex. The 'let-down' reflex is a response by the woman's body to the baby suckling. The stimulation of her nipple (and the woman's relaxation) triggers the release of the natural oxytocin hormone from her brain, causing her milk to 'eject', or flow freely. The 'let down' is also known as the 'milk ejection reflex', and usually starts around the time that the milk 'comes in' about 2 to 5 days after the birth.
Oxytocin is the same hormone that stimulates the contractions of the woman's uterus during labour (or the synthetic form, Syntocinon used to induce labour). Therefore, when a let-down occurs, the uterus also naturally contracts. This can cause slightly heavier, or brighter, bleeding after a feed in the first few weeks after the birth, and for some women it can cause strong afterpains for a few days (usually being more common with second or subsequent babies).
The let-down is usually triggered about 1 to 2 minutes after the baby starts feeding (or the woman starts expressing her milk). When the oxytocin hormone is released, it causes small muscle fibres around the breast's full milk ducts to contract for up to a minute or so, forcefully pushing the pooled milk down and out the nipple, often quite rapidly. A let-down can also happen if the woman is looking at her baby, thinking about her baby, if she hears her baby (or another baby) cry, or her nipples rub up against something. When the woman resumes sex after the birth, a let-down can also occur during touching of the nipples and the breasts and/or if she experiences an orgasm (take a towel with you!).
Many woman experience 'feeling' their let-down, although this is often not apparent until a week or two after the birth. Feeling a let down often coincides with the breasts settling in size and comfort (after the milk 'comes in') and the milk supply becoming more established but when the breasts are very full. Let-down sensations can be experienced for a few seconds, and will vary from being a 'tingling', 'sharp', 'warm' or a 'contraction-like feeling' in the breasts. For a few women, the let-down can be quite uncomfortable (although not usually consistently for every feed). Occasionally a woman may need to 'breathe through' the let-down, until it passes (a bit like breathing through a contraction during labour). Some women find the 'let-down' sensation quite pleasurable. A woman can also have 'multiple let-downs' throughout the one feed, but the sensation is often less noticeable with subsequent let-downs.
Not all women feel a 'let-down' (and just because you can't, doesn't mean it is not happening). The best way to tell if you are having a let down is by observing your baby feeding. As the milk starts to flow more rapidly (about 1 to 2 minutes after they start to suckle), their sucking pattern changes from being short frequent sucks, to long, deep 'gulping' actions. Milk may also leak from the other breast when a let-down occurs.
A let-down is an important component of achieving ongoing successful breastfeeding. This is because the baby is unable to fully empty the breast (and obtain all the milk they require), if the let-down does not occur. This can equate to the baby needing to feed for much longer and/or feeding more frequently than usual, as well as the gradual reduction in the amount of breast milk the woman produces
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