What's the Soft Spot on a Baby's Head?

Newborns’ bodies are full of surprises. One of the most intriguing is the little soft spots on your baby’s skull–what are those?! Don’t worry, you’re definitely not the first mama to google “baby's soft spot on head”. Called fontanelles, these spots will not be around forever—but while they are, they play an important role in your baby’s development.

So what exactly is a fontanelle? And what purpose does it serve? Let’s take a look.

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What is the soft spot on a baby's head?

Fontanelles are membrane-covered gaps on your baby’s head where the plates of their skull have yet to meet up with each other.

There are two main reasons these soft spots exist.

First, these soft spots allow for the bones in your baby’s skull to maneuver their way through the birth canal without causing any damage to their brain. Smart!

Second, they allow room for baby’s brain to grow.

In the first three months of your baby’s life, their brain grows from a third to half the size of an adult brain, expanding by about one percent every day.

By age two, it’s about three-quarters of an adult-sized brain.

The spaces in their skull allow for this expansion project to take place.

Where is the soft spot on a baby's head?

Every baby comes complete with six fontanelles—two of which you can likely feel as soft spots on your baby’s heads.

The larger one towards the front of the head is called the anterior fontanelle, and the slightly smaller one to the back is called the posterior fontanelle.

When does the soft spot on a baby's head close?

By the time your baby reaches the age of about two or three months, the posterior fontanelle—that’s the smaller spot at the back of their head—will begin to close.

When they are about eighteen months old, the larger spot towards the front of their head—or anterior fontanelle—should close.

What happens if you touch the soft spot on a baby's head?

Their fast-growing brains are protected by a kind of “helmet” made up of a protective, fibrous membrane.

That means your gentle touch is unlikely to hurt them.

In fact, there will be times when touching their fontanelles will be necessary, like when you’re supporting their head or washing their hair.

When should I be concerned about my baby's soft spot?

Changes—or lack of changes—to your baby’s soft spot can be unnerving.

Sometimes, what may look alarming is really just business-as-usual for the fontanelle.

If it looks like it’s pulsing, for example, it may just mean that blood is flowing to and around the area. Nothing to worry about.

In other cases, the appearance of their fontanelles can be a sign of a health complication. Here’s what to watch out for.

• A sunken soft spot. This can be a sign of dehydration, which can be quite dangerous in babies. Dehydration can be caused by feeding difficulties, fever, vomiting, and diarrhea. Signs include sunken eyes, fewer wet diapers, dry mouth, and fussiness. It’s a good idea to get to your healthcare provider as soon as you can if you suspect that your baby is dehydrated, particularly when they are very young.
• A swollen soft spot. If your baby has hit their head and you notice swelling, get them to a doctor. This could be a sign that they have suffered head trauma of some sort.
• A soft spot that sticks out. If you notice a lump around the soft spot areas, it’s important to call your doctor. A bulging soft spot may be a sign of fluid buildup, internal bleeding, or a tumor.
• A vanishing soft spot. If you notice that your baby’s soft spot seems to have disappeared—or you could never really notice it to begin with—it might be a sign that the bones have fused together early. This is called craniosynostosis and happens in about one in every 2,500 babies. If this is the case, your baby might need surgery. But it’s important to note that, even if their soft spots appear to have disappeared, it may not signal health complications. Some soft spots are just harder to feel. Either way, it’s no harm to check.
• A soft spot that doesn’t close. Like all parts of your baby’s development, soft spots tend to close at their own speed. If your baby’s soft spot hasn’t closed in the first two years, it could be a sign of a health condition called congenital hypothyroidism. This happens in about one in every 2,000 to 4,000 newborns, when the thyroid gland doesn’t develop properly or at all. If this is the case, your doctor will advise you about treatment options.

There’s a lot going on in the first few months of new mamahood. It helps to do this together. Let’s connect. Join us on Peanut.

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