A Guide to the Fontanelles

What they do, how to care for them, and what to watch for

Newborn baby boy in mom's hands

Nga Nguyen / Getty Images

Babies are born with soft spots on their heads. These soft, open areas of the skull are called fontanelles. If you do not have much experience with newborns, soft spots may make you nervous, but they are easy to care for and generally close correctly on their own.

What They Are

A fontanelle is an opening in a baby’s skull where the skull bones have not yet grown and joined together. The fontanelles have two main duties. 

  1. Birth: Fontanelles allow the bones of the skull to move so the baby’s head can change shape during delivery. The birth canal is narrow, and the movement of the bones helps the baby’s head to get through.
  2. Growth: A newborn's head is small, but it grows quickly over the first two years of life. The spaces between the skull bones leave room for the rapid expansion of the brain and head. 

The Different Fontanelles

Most people know about the soft spot on the top of a baby’s head, but there are more than just that one. A newborn actually has six of them

  • Anterior Fontanelle: There is one anterior fontanelle on the top of the head. It is the fontanelle that most people know as "the soft spot." It is the largest of the fontanelles. At birth, the average size of the anterior fontanelle is about an inch in diameter (2.1 centimeters), but it can be bigger or smaller.
  • Posterior Fontanelle: There is one posterior fontanelle at the back of the baby’s skull. This small opening is in the shape of a triangle and it usually measures less than ½ inch (1 centimeter) at birth.
  • Sphenoid Fontanelles: There are two of these, one on each side of the head. They are positioned toward the front of the skull near the temples.
  • Mastoid Fontanelles: There are also two mastoid fontanelles. There is one on each side of the head. They are toward the back of the skull behind the ears.

When They Close

The skull bones do not completely seal up during childhood because the brain and body still need room to grow. However, once the bones grow to the point that they fill in the open space and the doctors can no longer feel them, the fontanelles are considered closed. Fontanelles do not all close at the same time. The process can take two years or longer. The six fontanelles close in this order: 

  • Posterior: Between six weeks and three months
  • Sphenoid: By six months
  • Mastoid: Between six and 18 months
  • Anterior: Starts to close at six months and can no longer be felt between 18 months and two years. 

The list above is a range of average closure times. A fontanelle can close earlier or later and still be normal.

How to Care for Fontanelles

Caring for your baby’s fontanelles involves learning what to watch for and understanding what’s normal. Here are some of the things you should know. 

  • Your baby’s fontanelle should look flat against her head. It should not look like it is swollen and bulging or sinking down into your child’s skull. 
  • When you gently run your fingers over the top of your child’s head, the soft spot should feel soft and flat with a slight downward curve.
  • When your child is crying, vomiting, or lying down, the fontanelle may look raised or like it’s bulging. As long as it goes back to normal once the baby is upright and calm, it’s OK and not a truly bulging fontanelle. 
  • Sometimes the fontanelle can look like it’s pulsating. It is the baby’s pulse visible in the fontanelle and moving with the heartbeat. You can see it more easily if the baby doesn’t have much hair or his hair is very light. It might seem strange or scary, but it’s normal. 

You can be gentle, but you don’t have to be scared to touch or care for your child’s head. There may be a space between the bones, but a tough membrane over the opening protects the soft tissue and the brain. So, you can:

  • Touch your baby’s head
  • Wash her head and scalp
  • Use a baby brush or comb on her hair  
  • Put on a cute headband 
  • Allow your other children to hold and touch the baby (with supervision)

Concerns

The fontanelles can give you clues about your child’s health. Here are what some changes in the soft spot could mean:

Sunken

It is normal for the fontanelle to have a slight inward curve. But, if it sinks down into your baby’s head, it could be a sign of dehydration. Dehydration in newborn and young infants is dangerous. It happens when a baby doesn’t get enough fluids, or the child is losing more fluids than she’s taking in. Your child can become dehydrated if he 

  • Does not breastfeed or bottle feed well
  • Gets sick with diarrhea, vomiting, or a fever
  • Spends too much time in a hot environment and overheats

Other signs of dehydration include not producing enough urine, excessive sleepiness, irritability, dry mouth, and crying without tears. If your child is showing signs of dehydration, call the doctor right way.

Bulging

As mentioned above, if a baby has a slightly raised fontanelle when she’s crying it doesn’t necessarily mean that anything is wrong. However, if the baby’s fontanelle continues to bulge when the baby stops crying, or it feels swollen and hard when the baby is resting, it could be a sign of a health problem. A bulging fontanelle could mean there is a build-up of fluid or swelling in the brain. These are dangerous conditions that require immediate medical treatment.

Very Large

A soft spot that is abnormally large or does not close within the expected time frame can be a sign of certain medical conditions such as hypothyroidism, Down syndrome, or rickets. Your doctor will examine your baby’s health and fontanelles at birth and continue to monitor your baby as he grows. If there is an issue, the doctor will let you know. Of course, if you are worried about the size or closure of your baby’s fontanelle, you should feel comfortable to discuss it with the doctor.

Closes Too Soon

It is rare for the fontanelles to close too early. But, if the skull bones join together and close too soon, it could cause some issues for the baby. The premature fusing of the skull bones is a condition called craniosynostosis. Craniosynostosis can affect the brain’s growth and the shape of the baby’s head. It could also cause pressure to build up inside the baby’s skull. If it’s mild, it may not need treatment, but more serious conditions usually require surgery. Sometimes, the soft spots cannot be felt easily and seem closed, but they are still open. The doctor will monitor your child by checking the fontanelles and measuring your baby’s head at each well-child appointment.  

Fontanelles and Head Shape

The fontanelles play a role in the shape of a baby’s head. Since there’s space for the bones to move, any pressure on the skull can influence its shape. Two common head shape issues are: 

Molded Head

Fontanelles allow the bones of the skull to move during birth. The length of time the baby’s head stays in the birth canal and how much pressure there is on the skull can determine what the baby’s head looks like after the delivery. Sometimes the head appears cone-shaped or even pointy. It’s nothing to worry about, though. Within a few days, the baby’s head should turn into the more rounded shape that you were expecting. 

Flat Head

Until the fontanelles close and the bones of the skull join together, the shape of the baby’s head can change. An issue that comes up is the flattening of the back or the side of the head called plagiocephaly. It's from babies laying in the same position on their back or their side. The “back to sleep” campaign is important, and it works to lower the risk of sudden infant death syndrome (SIDS). But it can increase the chances of plagiocephaly.

If your baby sleeps on her back at night in the crib, then sits on her back in a carrier and a car seat during the day, the back of her head will flatten out from the pressure of laying on it all the time.

To prevent pressure in one spot, change your baby’s position during the day. Place your child on her back to sleep, but then give the back of her head a break when she’s awake. You can carry her in your arms or an infant sling, let her spend some time on her tummy and give her things to look at that will turn her head from side to side when she’s on her back.

A Word From Verywell

The doctor will check your baby’s fontanelles at birth. Monitoring will continue whenever a doctor, midwife, or nurse examines your child, and you can check your baby's soft spot at home. While there isn’t anything special you need to do to care for fontanelles, it’s good to know a little about them.

Understanding why they’re there and what they should look like can help you feel more confident as you care for your child, and even help you keep the baby’s head from becoming flat in one spot.

Your baby’s soft spot may seem scary at first. You might not want to touch the top of your baby's head, either because you don’t want to harm the baby or you don’t like how it feels. But touching the fontanelle won’t hurt the baby and it can give you important information about your child’s health. Of course, if you are worried or have any questions about your baby’s fontanelles, you can always talk to the doctor. 

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