When breastfeeding mothers talk about their milk coming in, they are referring to the onset of production of transitional milk, the creamy milk that immediately follows colostrum. Transitional milk is produced anywhere from about two to five days after birth until ten to fourteen days after birth. Because your breasts will supply a much greater amount of transitional milk than colostrum, your breasts will become larger and firmer during this stage. This new fullness may feel uncomfortable at first and may make it more difficult for your baby to latch on to the breast correctly. Sometimes expressing a small amount of milk by hand will help to soften the areola enough to make it easier for the baby to latch. The drops of milk on your nipple also will encourage your baby to feed. Breastfeeding will ease the pressure in your breasts and make you feel more comfortable. As your baby latches on and begins to breastfeed steadily, you may notice a tingly pins-and-needles sensation.
The difference between foremilk and hindmilk
Breast milk goes through changes from the end of pregnancy through the first few weeks after your baby is born. These changes are often called stages or phases. Colostrum is the first stage, transitional milk is the second stage, and mature milk is the final stage of breast milk. In the beginning, your breast milk starts out as colostrum.
Is there milk in my breasts at birth?
Milk production begins around the midpoint of pregnancy. Colostrum is being produced from about weeks of pregnancy, although many mothers are not aware that the milk is there since it may not be leaking or easy to express. Colostrum is the early, concentrated milk that is full of nutrients and disease-fighting antibodies — it provides everything that your baby needs in the early days after birth. Milk production normally begins to increase biochemically between 30 and 40 hours after delivery of the placenta, but it may take a little while for the changes to become apparent to the mother. Keep in mind that many women experience their milk coming in as a gradual change, rather than a sudden one. Research indicates that this timing is hormonally controlled — it does not require that baby be breastfeeding at all.
From around the time your baby is a month old, your breast milk is fully mature. Soon after it reaches maturity, your milk starts to contain higher quantities of some components that protect your baby against bacterial and viral infections. But the biggest fluctuation occurs if you or your baby pick up an infection. Then the proportion of white blood cells in your milk will rocket to fight it off. Like all stages of breast milk, mature milk is a living fluid. And yet you never have to think about it, because your body produces the formulation your baby needs. The concentrations of fat in pre- and post-milk depend on how much milk the baby has taken from the breast. So at one time of day the pre-milk could have a higher fat content than the post-milk at another time of day. All milk contains the sugar lactose, but breast milk also contains more than human milk oligosaccharides. Similarly, all milks contain fats, but the blend of fats in mature human milk is uniquely complex.