The Biology of Breast Milk
It's pretty amazing that your body knows when to start producing breast milk. In fact, pregnancy hormones trigger the milk glands in the breasts to start working as early as the first trimester (expect to go up a cup size or two!)
After you give birth, the estrogen and progesterone levels in your body dip and the hormone prolactin increases, prompting the milk glands to produce milk. Who knew all that was going on?!
The first breast milk your body produces is called colostrum (otherwise known as liquid gold!) and it has special antibodies (a.k.a. super powers!) that help to boost your baby's immune system. Then, a few days after childbirth, your breasts will get busy producing transitional breast milk. But be patient—a week or so after giving birth, your breasts will produce mature milk.
Oxytocin, the hormone that triggered contractions during childbirth, helps you out yet again;this time by triggering the milk "let-down" reflex (don't be surprised if your boobs feel all tingly!) Your pregnant and post-partum boobs are pretty awesome—they are working overtime (even while you sleep!) to produce enough breast milk to feed your new baby.
But it's not just up to the magic of your boobs, YOU have a part in creating an abundant milk supply too. According to lactation consultant Amy Bourne, "By breastfeeding early and often the first few days, you're sending your body a message to create lots of milk." It's a pretty amazing process!