There's A Biological Reason Babies Do The 'Breast Crawl'

If you’ve been lucky enough to witness it, watching a newborn crawl up to the breast and latch on is one of the most amazing things you’ll ever see. It’s a phenomenon called “the breast crawl” and most healthy babies are able to do it without any help at all. A mom just places their newborn on their belly or chest, waits patiently, and eventually the baby scoots and shimmies up to the breast and is able to latch on, all by themselves.

I was able to do the breast crawl with my second baby, and it was one of the most memorable moments of my life. I’ll be honest, even though I’d learned lots about it beforehand, I wasn’t sure if it would really work or that my baby would know what to do (after all, he’d just been born!). But after a few minutes of just hanging out there, he pressed his tiny foot into my belly and started moving toward my breast. After a few minutes, he began licking my nipple and trying to suck.

If you haven’t had the honor of watching a baby do this live and in person, no worries. You can watch it all unfold here. (Warning: Your ovaries might very well explode.)

Totally unbelievable, right? You’re probably wondering how on earth this baby knew what the heck to do. Well, there have been lots of theories about how the phenomenon works, including the idea a baby’s smell, taste, vision, and instincts all work together to guide them to the breast.

But a 2017 study might offer the best evidence yet of how this whole thing works, and it will blow your mind. It all has to do with body temperature: the mom’s nipples actually heat up so that her baby can find them, while the baby’s body temperature decreases to make mom’s nipples seem even warmer.

The study, published in Acta Paediatrica, looked at 41 moms who gave birth at a hospital in Italy between January and February 2015. The moms all intended to breastfeed and were considered low-risk pregnancies. After birth, their babies were placed on their chests for at least 15 minutes and allowed to crawl to the breast to latch on.

The moms’ temperatures were assessed at three points: about 6 hours before they gave birth and at one and two days postpartum. The researchers examined both the moms’ nipples as well as the surrounding skin.

Now, get this: Even before giving birth, the moms’ nipples were 0.4 degrees higher than their surrounding skin. But on the day they gave birth, the moms’ nipple temperatures rose 0.9 degrees higher than their surrounding skin, and by the second day after giving birth, the temperature had risen 1.1 degrees higher than the moms’ surrounding skin.

But it wasn’t just the nipple temperature itself that was significant here. The researchers also measured the itty-bitty babies’ lips and foreheads. They found that on the first two days after being born, the babies’ lips were cooler than their foreheads (2.2 degrees coolers on the first day; 1.8 degrees cooler on the second day).

This meant that when you compared the moms’ nipple temperatures to their babies’ lip temperatures, there was a 3 degree difference – i.e., the mamas’ nipples heated up while the babies’ lips cooled down.

The theory is that cold baby lips are drawn to warm mama nipples, which makes total sense when you think about it. And the mind boggling thing here is that all of this happens without anyone having to do anything about it. Biology sets things up so that babies are naturally drawn toward their warm, milky mamas.

Or, as the study researchers explain it: “These findings demonstrate, for the first time, that a temperature gradient may support mother‐infant thermal identification and communication in the breast crawl and in the natural progression of the continuum from birth to breastfeeding.”

The researchers also surmise that the “thermal cue” between the mother’s nipple and the baby’s lips is one of several factors all working in concert to make the breast crawl possible. For example, they note the previous research showing that babies react to the smell of moms’ nipples at birth, and they hypothesize that the warmer temperature of the nipple only enhances these smells.

Oh my goodness. Aren’t women’s bodies just freaking incredible?

Now I know it’s not possible for every mom and baby to try the breast crawl — and certainly not all moms are even interested in doing so. But I urge all moms to give it a try if possible. It’s a great way to bond with your baby, get breastfeeding off to a good start, and of course to marvel at the amazingness that is human biology.