You’ve probably already heard that you need to be very gentle with your baby’s skull. But do you know why? The bones of your baby’s head have not yet fully matured. The skull has fontanelles , soft tissues that connect the bones of the head. What are they? What are they for? Why should you pay close attention to them? When do they close? We’ll help you see things more clearly and, above all, better understand what fontanelles are.

What are the fontanelles?

Your baby's skull is soft in certain areas, known as fontanelles. These areas of your child’s head play several roles in your baby’s arrival and development.

The fontanelles, the definition

A fontanel is a membrane located between the bones of the skull in infants . The bones of your baby's skull are not fused, but they are connected by a soft membrane. There are two main fontanelles in your little one’s skull. The anterior fontanelle, or large fontanelle, is located at the front of the head and measures between 3 and 6 cm in width. The posterior fontanelle, or small fontanelle, is located at the back of the head and is approximately 1 cm wide. There are also paired fontanelles on each side of the skull that play a minor role. They naturally close after a certain age.

What are fontanelles used for?

The fontanelles have two functions:

They facilitate childbirth because they allow your baby's skull to deform slightly during delivery. This deformation is temporary ; it lasts from a few hours to a few weeks and does not damage the brain.

They enable your baby’s brain growth , which is very rapid until about 2 years old. The size of a child's brain doubles in just a few months, and these flexible tissues allow for this fast development.

Are the fontanelles fragile?

A fontanel is a soft membrane that connects two bones of your baby's skull. It is more fragile than bone, but you can still touch it . You simply need to be a bit more careful until it closes. You can gently stroke your little one’s head without fear, as the membranes protect the brain.

We recommend taking extra precautions, especially during handling. But again, since you shouldn’t press on them, you can touch them. If you’re really concerned, you can put a hat on your baby. At birth, a hat helps your little one stay warm, as heat escapes through the skull, and it also protects the fontanelles. You can keep this habit during the first few weeks of your little one’s life. In winter, you may prefer hats made of soft, slightly warm materials. In summer, choose lightweight, breathable fabrics so your baby doesn’t get too hot.

Why is the examination of the fontanelles routine?

When your baby has a medical check-up, their doctor or pediatrician examines the fontanelles. This allows them to see whether they are closing properly and to check for any abnormalities. They can verify proper brain growth by measuring your little explorer’s head. Examining the fontanelles can help detect certain conditions.

It can happen that the anterior fontanelle swells when your child cries; this is perfectly normal. If it remains swollen while your child is calm and has a fever , then you should consult a healthcare professional.

Conversely, the posterior fontanelle may sink slightly at the back of the skull. This can be a sign of dehydration. It’s best to make sure your baby is drinking well and to discuss this with your doctor or pediatrician.

Pathologies related to the fontanelles are very rare. If your baby has a big head, it is not necessarily a sign of a problem. Babies have proportionally larger heads than adults. As always, if you have any doubt or concern, don’t keep your questions to yourself—talk to qualified professionals who can reassure you and provide the right information.

At what age do the fontanelles close?

The small fontanel at the back of the head closes around 2 months of age . Its main function is to facilitate your baby’s birth, so it doesn’t stay open for very long. It may take a little longer to close; if that’s the case, discuss it with your child’s healthcare professional.

The anterior fontanel, the one at the front of the skull, closes between 8 months and 2 years. It has a dual function. It helps during birth, but it also allows the brain to grow and the head to increase in size. If it closes around 8 months, it does not prevent completely normal brain development. And if it takes a little longer, you can discuss it with your pediatrician or doctor.

The paired fontanelles close between 3 and 6 months for one and around 18 months for the other. As they close, they allow larger bone surfaces to form on your child’s skull.

The fontanelles are membranes that make a baby’s skull soft and therefore help with birth and brain growth . You can touch them without fear, but you still need to be gentle with these areas. If your little one cries, the anterior fontanelle may swell, but it’s not a big deal; it will quickly return to its original size.