About the fontanelle

About the fontanelle

What are fontanelles?

Unlike adults, babies have skull bones that are not firmly joined together. The spaces between the skull bones are important as they allow the bones to move, and even overlap, when the baby passes through the birth canal. These spaces also allow room for the baby’s brain to grow.

You may notice one such space, or fontanelle, at the front on top of the head and another smaller fontanelle at the back of the head.

Over time, the fontanelles harden and close. The fontanelle at the back of your baby’s head usually closes by the time your baby is 2 months old. The fontanelle at the top usually closes sometime between the ages of 7 months and 18 months.

Observing the fontanelle

Some parents may feel anxious about touching the fontanelles. However, there is no need to worry or to avoid touching the fontanelles, as they are protected by a tough membrane or layer of tissue.

Changes or abnormalities in the fontanelles may provide clues about your baby’s development and health. This is why it’s normal for your baby’s doctor or nurse to examine your baby’s fontanelles during check-ups. For instance, delayed fontanelle closure or an enlarged fontanelle can be associated with a range of medical conditions.

Sunken fontanelle

When you touch the fontanelle, it should feel firm with a slight inward curve. Many parents will worry about the fontanelle being ‘sunken’ (drawn in) and that this is a sign of being dehydrated (does not have enough fluid in their body). However, while a sunken fontanelle can occur when your baby is severely dehydrated there are many other signs of dehydration that happen before a fontanelle becomes sunken, such as fewer wet nappies and being less alert and responsive, and usually dehydration occurs when the baby is not feeding well or losing fluid through vomiting or diarrhoea. See your doctor right away if your baby has any of these signs of dehydration.

Bulging fontanelle

Your baby’s fontanelle may bulge or look raised when they cry but return to flat or slightly curved in when your baby is not crying and is in a head-up position. This is not a cause for concern.

A bulging fontanelle that does not return to normal may be a sign of a serious condition, such as an infection or swelling in the brain. See your doctor immediately, especially if your baby has a fever or is unusually sleepy.