Why do babies have a soft spot?
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That soft spot on a baby's head isn't actually bone. New parents touch it, and often snatch their hand right back. It feels soft because there's simply no bone there.
It's a gap left on purpose, between several skull bones. A tough membrane covers the gap, with scalp and hair on top. This spot is called the fontanelle. The big one sits on top, toward the front, shaped like a diamond; there's a small one at the back.
Why leave a gap at all? Start with the day of birth. A baby's head is the biggest part of its body, and the birth canal is a little narrower. At this point the skull isn't one hard shell, but several thin plates joined by soft seams.
Under pressure, the plates slide and their edges overlap, so the head narrows and can squeeze through. That's why some newborns arrive with a slightly pointy head, which usually rounds out in a few days. Once the baby is out, the gap keeps working.
At birth, a baby's brain is only about a third the size of an adult's. In the first three months alone, it grows by more than sixty percent. It's a bit like laying a wooden floor at home.
Installers leave a gap along the walls, so when the wood swells, it has somewhere to go. The skull plates are the floorboards; the seams and fontanelles are that gap. As the brain grows, the plates move outward with it, and new bone slowly fills in at the edges.
Floorboards can't overlap, but skull plates can, and that's what gets the head through birth. The small fontanelle at the back closes within two or three months. The big one on top usually takes until after the first birthday, sometimes until two, to fill in.
So, can you touch it? Yes. Gentle touching, washing and brushing are all fine; that membrane is much tougher than it looks. Sometimes you'll see it pulse; that's the heartbeat, and it's normal too.
Just don't press hard. If it looks clearly sunken, or bulging and tight, see a doctor and follow their advice. So that soft spot isn't missing bone; it's room saved for being born, and for growing. When your baby was born, was the head round, or a little pointy?
That soft spot
isn't bone at all
It's a gap left on purpose between the skull bones. A tough membrane covers it, with scalp and hair on top.
It's called a fontanelle. The big one sits on top, toward the front, shaped like a diamond. There's a small one at the back. Every baby has them.
On the day of birth, the skull folds up
A baby's head is the biggest part of its body, and the birth canal is a little narrower.
At this point the skull isn't one hard shell. It's several thin plates joined by soft seams. Under pressure, the plates slide and their edges overlap, so the head narrows and can squeeze through.
That's why some newborns arrive with a slightly pointy head. It usually rounds out in a few days.
Like the gap left around a wooden floor
At birth, a baby's brain is only about a third the size of an adult's. In the first three months alone, it grows by more than 60%.
It's a bit like laying a wooden floor. Installers leave a gap along the walls, so when the wood swells it has somewhere to go. The skull plates are the floorboards; the seams and fontanelles are that gap. As the brain grows, the plates move outward with it, and new bone slowly fills in at the edges.
Floorboards can't overlap, but skull plates can, and that's what gets the head through birth. The head isn't the only soft part of a baby: see why babies are so bendy.
It closes after the first birthday
The small fontanelle at the back closes within two or three months. The big one on top usually takes until after the first birthday, sometimes until two, to fill in. A bit earlier or later is common, and the doctor checks it at well-baby visits.
So, can you touch it?
Just don't press hard. If it looks like either of these, see a doctor and follow their advice.
Quick check
What is a baby's soft spot, really?
It's like the gap left around a wooden floor: space between the plates so they can overlap at birth and spread as the brain grows.
