When you know how breast milk is made, it is easier to understand why breastfeeding babies nurse frequently. At first, the hormones that change after you give birth are responsible for milk production. After your baby is about 1 or 2 weeks old, your baby's ability to fully and frequently empty the milk from your breasts plays a greater role in the amount produced.
While you are still pregnant and just after birth, your breasts make colostrum. It is often dark yellow or orange, so people call it "liquid gold." This is a thick, rich food that is small in volume. It is important to remember that your baby's stomach is very small and does not need a large amount of milk to be filled. If your baby seems satisfied and is making the correct number of wet or dirty diapers, you can feel confident that your body is making everything that your baby needs. Keep nursing when your baby is telling you that he or she is hungry, and your body will respond to the signals to make more milk.
Hormones and breast milk
After your baby is born and the placenta is delivered, a drop in the pregnancy hormones allows the hormone prolactin to begin to work. Prolactin "tells" the breasts it is time to start making large amounts of milk. A mother feels the result of prolactin when her milk "comes in," usually when her baby is about 3 to 5 days old. Increased milk production typically occurs at this time even if a baby has not been breastfeeding well or often. However, frequent breastfeeding can speed up the process of establishing increased milk production. Occasionally, a mother have a delay in the production of large amounts of milk.
After milk has come in
Ongoing, long-term milk production depends mostly on milk removal. The more often and completely it is removed, the more milk the breasts make. The opposite is also true. When milk is removed less often or not enough is removed, the breasts get the signal to slow milk production and make less.
To fully empty the breast, a baby must have a good latch. A baby must latch deeply onto the breast and use the structures in his or her mouth to create intermittent suction, compress the breast with his or her mouth, and swallow. When your baby does this, your body will respond to the signal by releasing the hormone oxytocin. This leads to the release of larger volumes of milk—a process known as milk "let down."
You can use milk expression to fully empty your breasts, if your baby cannot or you are separated from him or her. You can express milk by hand by compressing the breast tissue with your hands. You can also express milk with a breast pump.