How Does Your Body Know When To Nurse? Experts Explain

As anyone who has ever breastfed a baby can tell you, sometimes it seems like your breasts have a mind of their own. Like, for example, when milk leaks everywhere, or you wake up with rock-hard breasts after your baby sleeps through the night. And then there are the moments when your body seems to know when it's time for your baby to eat, way before they cry. Yes, your body knows when to nurse. And, yes, it's about as awesome as it sounds.

Turns out, lactation isn't some sort of super secret magic trick or a special kind of sixth sense. Instead, it's actually some pretty amazing — and complex — biology at work, involving communication between your body, your baby, and your brain. According to Certified Nurse Midwife, Joyce King, CNM, FNP, PhD, your body starts getting ready for nursing before your baby is even born, producing hormones that make your breasts feel oh-so tender during pregnancy (and causes them to grow a cup size or two). According to Mayo Clinic, once your milk comes in, your body should produce milk on demand, so the more often you feed the more milk your body should produce.

However, as human milk researchers Sooyeon Lee and Shannon Kelleher explain in the American Journal of Physiology - Endocrinology and Metabolism, lactation is not that simple, biologically speaking. Your ability to lactate and produce enough milk actually depends on a variety of complex factors. In other words, there's a number of things that might stop your body from getting the message that it's time to nurse.


When you think about breastfeeding, you probably focus on what's happening in your breasts. According to Mayo Clinic, your ability to make breast milk depends largely on demand, a.k.a how often and how much you nurse or otherwise remove breast milk from your breasts by either pumping or expressing. According to BabyCenter, this is why your breasts might feel hard and full after an unexpected break from your baby, if you drop a nursing or pumping session, or when you wean your baby.

As King explains in the Journal of Midwifery and Women's Health, your body knows when it's time to nurse because of what's happening in your brain, not your breasts. Starting during pregnancy, your brain produces a hormone called prolactin that causes your breasts to prepare to lactate. She adds that until you give birth, and your placenta is removed, other hormones — progesterone and estrogen — tell your body to not make milk just yet. Which is why some breastfeeding moms experience supply issues if they get pregnant and/or take hormonal birth control.


According to King, a variety of other factors can influence your body's ability to make and dispense breast milk, including getting enough to eat and drink, your baby's ability to remove milk, and even things like your thyroid health, stress, and insulin production. That's why your milk supply might drop when you're overwhelmed and stressed out. According to the Fed is Best Foundation, moms with thyroid disorders or diabetes might be more at risk for delays in their milk coming in and/or experiencing under supply.

Lee and Kelleher explain further in the American Journal of Physiology - Endocrinology and Metabolism, citing that researchers now know that your body's ability to produce enough milk to feed your baby is anything but simple. Everything from your genetics to your environment can throw a wrench in such a complex biological process. Which might be why, according to the same article, 50 percent of breastfeeding moms end up weaning early because they don't make enough milk.

Fortunately, for parents and babies alike, one way to help your breasts do their thing is actually snuggling, according to an article in the Journal of Perinatal Education. Skin-to-skin contact with your baby signals your brain to produce oxytocin — the hormone responsible for milk ejection. American Academy of Pediatrics (AAP) suggests, if you and your baby are well enough after delivery, you have skin-to-skin contact with your baby as soon as possible to help with bonding and breastfeeding. As if you needed another reason to snuggle, right?


Seeing your baby, holding them, and even smelling them can all play a role in the release of oxytocin, too. The website suggests that you try looking at pictures of your baby, and bring along something that smells like your little one, like a blanket or their baby lotion, to send warm, fuzzy, milk-producing messages to your brain and breasts during any pumping sessions you spend away from baby.

While knowing the biology behind breastfeeding might make it sound scary and overwhelming, the good news is that, as Lee and Kelleher note, the more we know about how lactation works, and the problems some breastfeeding moms face, the more we can do to find solutions to some of those problems and support breastfeeding moms in feeding their babies. So, yeah, science rules.
