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How Does a Newborn's Skull Grow and Change Shape?

Dr. Vincent Farrar, DC, DICCP, CACCPJuly 21, 20263 min read

A newborn's skull arrives as separate plates with open seams so it can keep pace with rapid brain growth, shaped from inside and by movement.

How Does a Newborn's Skull Grow and Change Shape?

A newborn's skull isn't a finished object, and it isn't really trying to be one.

Start with the reason. At birth, a baby's brain is about a quarter of the size it will eventually be. By the end of the first year it's roughly half. That's an enormous amount of growth crammed into a very short stretch, and the container has to keep up. Which is why a baby's skull arrives as separate plates with the seams still open, rather than as one solid dome.

So where does the shape come from?

From the inside, the brain. The growing brain works as an expanding force, and that force is part of what stimulates the skull to develop around it. The brain isn't a passenger sitting inside a case that was built for it. Push from underneath, and the plates spread and lay down bone at the edges.

From the outside, muscle. Every time she lifts and holds her head up, the muscles on the back of the neck pull on the back of the skull, and that pull is part of what rounds it out. That's tummy time, and car seat head control, and the thousand small head lifts nobody counts.

Two forces. One pushing out, one pulling in.

The picture I use is a balloon inflating inside a loose net. The balloon pushes. The net pulls back. And the shape you end up looking at is the argument between them, settled a little more each week.

I like this one for parents for a specific reason, and it has nothing to do with anything we do. It changes what you're looking at when you look at your baby's head. It stops being a finished feature you were handed, like an eye color, and becomes something closer to a photograph of a process still running.

There's a limit, and it matters. This is anatomy. It's a description of how a skull comes to have the shape it has. It isn't a claim that anybody reshapes a head with their hands, and it isn't a claim about influencing how a brain grows.

What I check is the movement end of it, which is the modest part. Does the neck extend and rotate freely both directions? Is one direction easier? That's observable, measurable, and it's the piece of this picture that belongs in an exam room.

Her head is a growing structure, shaped by what's inside it and by how she moves.


Keep reading: Babies and Development

Individual results vary. Chiropractic care does not diagnose, treat, or cure any disease or condition. This information is educational and not a substitute for medical care. Sláinte provides wellness chiropractic care and works alongside your medical team.

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