What To Know About Baby’s Fontanelles (aka soft spots)

When you’re a new parent, you know that your baby needs you for a lot of things. From help burping to safe sleep practices to proper feeding, your baby relies on you to learn their cues and keep them safe and healthy.

So when you realize that your itty-bitty bundle of joy has bones in their noggin that are not entirely fused together, it’s natural to wonder if those soft spots (also called fontanelles) are as they should be.

In truth, your baby’s fontanelles rarely require much attention. But they are an important reminder of just how fragile your infant is.

That’s why, if something changes — like the fontanelle looks sunken or bulging — you may worry there’s something wrong.

A change in the fontanelle isn’t always a major problem, but it can sometimes reveal areas for concern, says pediatrician Brigitta Moresea, MD. “Your baby’s soft spots are a good indicator of the baby’s potential hydration status and brain status. They’re like automatic pressure sensors.”

What exactly are fontanelles? And what do you need to know about them? Dr. Moresea shares advice.

What are the fontanelles?

When babies are born, their skulls aren’t fully formed. That’s normal. And it’s like that for a reason.

“Babies’ heads aren’t entirely fused together,” Dr. Moresea explains. “That’s what allows the baby’s head to travel more easily through the birth canal. It also allows for rapid head growth during the first year of their life.”

The fontanelles are the diamond-shaped soft spots in between baby’s skull plates that haven’t yet joined together. These soft spots are covered in skin and protected by a layer of tough membranes. So even though they’re called “soft spots” they’re still pretty hardy. As long as you’re using normal and cautious baby care and baby handling practices, you’re not going to hurt them.

There are two main fontanelles.

The anterior fontanelle is right on top of your baby’s head. It’s the one you most typically think of when you hear about “baby’s soft spot.” On average, it’s about 2.1 centimeters (cm) in diameter. That’s about the size of a penny. The anterior fontanelle typically closes soon after your child’s first birthday.

The posterior fontanelle is smaller and is on the back of baby’s head. The average size of the poterior fontanelle is about the size of a pencil eraser (0.5 cm in diameter). It typically closes by the time your baby is just two or three months old.

When to worry about fontanelle

Sometimes, a baby’s fontanelle can be a window into potential concerns with their growth and development.

Checking baby’s fontanelle is a regular part of visits with a pediatric healthcare provider, like during their well-child checkups. The baby’s provider may measure their head and lightly feel baby’s fontanelles as part of their standard exam,

If you or a healthcare provider notice a change in baby’s fontanelles, it’s worth paying attention.

Dr. Moresea explains some common changes in the fontanelle and what they may be telling you about your infant’s health.

Sunken fontanelle

Baby’s soft spot should be mostly flush with the rest of their noggin. So if it divots in like the top of a golf tee, it may be cause for concern.

“A sunken fontanelle is often a sign of dehydration,” Dr. Moresea shares. “It may occur if your child is sick and not getting enough fluids.”

Other signs that your baby may be dehydrated include things like:

• Having fewer wet diapers than usual.
• Having a dry mouth or lips.
• Being extra sleepy or fussy.
• Few or no tears when crying.

What to do about a sunken fontanelle: Encourage baby to drink more by offering extra bottles or breastfeeding sessions. See a child’s healthcare provider, like a pediatrician, if the sunken appearance persists and you can’t get your baby to take in more fluids. Also contact your provider if your child is showing other signs of illness, like a worrying fever.

Bulging fontanelle

If baby’s fontanelle is bulging or looks swollen, it may be cause for concern.

For example, after a fall, a swollen soft spot is sometimes a sign of head trauma. It may also be accompanied by vomiting.

If baby’s fontanelle is bulging and there’s no reason to think they’ve recently hit their head, there may be other reasons to seek medical care.

Bulging fontanelle can be a sign of viral or bacterial infection.

In rarer cases, bulging can be a result of fluid buildup in the brain — a condition called hydrocephalus. It can cause rapid head growth and can make the soft spot look “full,” Dr. Moresea says. A bulging fontanelle may also stem from conditions internal bleeding or a tumor or mass causing pressure in the head.

What to do about a bulging fontanelle: If your child’s soft spot is swollen, contact your child’s healthcare provider, Dr. Moresea advises. If the bulging is the result of an injury to their head, seek prompt medical attention, such as your local emergency room. Also seek emergency attention if a bulging fontanelle comes with symptoms like fatigue, vomiting or changes in baby’s temperament — like if they’re extra sleepy or fussy.

Disappearing soft spot

In most babies, soft spots are pretty obvious. You can feel them with your hand using very gentle pressure. You may even feel their pulse when you feel their fontanelles.

What do you do if you can’t feel baby’s fontanelle, though? Can the soft spot close up too quickly?

Some babies have what Dr. Moresea calls a “quiet fontanelle.” That’s to say, a soft spot that’s less noticeable.

As long as your child’s head is growing normally, there’s not much to worry about if your baby’s soft spot is less pronounced, Dr. Moresea shares.

If their healthcare provider is concerned that your baby’s soft spot has closed too soon, though, they may suggest an imaging test to make sure.

“Occasionally, the skull bones do close earlier than normal on one side. That causes a condition called craniosynostosis,” Dr. Moresea reports. “Depending on which bones fused, baby may develop an asymmetric or 'abnormal’ head shape. For example, sagittal craniosynostosis, the most common form, results in a longer head that is shaped somewhat like a football.”

What you should do: Talk with your child’s healthcare provider if you believe their soft spot is closed prematurely. Children with craniosynostosis may need to wear a specialized medical helmet to help reshape their skull. Some babies may also need surgery to open the fused bones and reshape their skull.

Soft spot that doesn’t close

Soft spots that are bigger than average or stay open longer than about a year can sometimes be a sign of a medical condition.

Researchers say that large fontanelles and fontanelles that don’t close when they’re expected to can be associated with conditions like:

• Down syndrome.
• Achondroplasia, a growth condition.
• Congenital hypothyroidism.
• Rickets, a condition that causes warped bones and bones that break more easily.
• Abnormally high amounts of pressure in their brain.

It’s important to note that these conditions come with other symptoms. No need to prematurely rush to conclusions if your baby is otherwise developing normally.

What you should do: Talk to your child’s healthcare provider about the development of their fontanelle and any other concerns you have about your baby’s growth and development.

The bottom line? Your baby’s soft spot can be an indication of their overall health. But it’s just one way to assess whether your child is growing as expected.

Talk with your healthcare provider if you have any questions or concerns. Keep up with regular well-child checkups to make sure your little one is on track for healthy development.