A Guide to Your Baby's Soft Spots or Fontanelles

A diagram of the fontanelles of a baby's head.

Verywell / JR Bee

To understand how a baby maneuvers out of the pelvis, it's helpful to learn a bit about the fetal skull. The bones of a baby's skull are not fused. Instead, there are spaces between the bones. Suture lines on the skull indicate where these soft spots, called fontanelles, are located. These spaces allow the bones to overlap as the baby moves through the pelvis in late pregnancy and during labor.

Learn why fontanelles are important, how to care for them, when they close, and what to look for if you are concerned about them.

What Are Fontanelles?

A fontanelle is an opening in a baby’s skull where the bones have not yet grown together. Although they may seem like undeveloped areas of your baby's head, fontanelles are actually a critical part of normal infant development. They serve two important roles for your child.

  1. Birth: By leaving space for the bones of the skull to move during delivery, the fontanelles allow your baby's head to fit through the narrow birth canal without damaging their brain.
  2. Growth: A baby's head grows more quickly over the first two years than at any other time in their life. The spaces between the skull bones leave the room needed for expansion of the brain during this period of rapid growth. 

Types of Fontanelles

Most people know about the large soft spot on the top of a baby’s head, but it's not the only one. A newborn has two fontanelles: 

  • Anterior fontanelle: Located on the top of the head, this diamond-shaped fontanelle is the one that most people know as "the soft spot." It measures about 1 to 3 centimeters at birth, but can be larger or smaller.
  • Posterior fontanelle: This smaller opening at the back of the baby’s skull is triangular in shape. It usually measures less than ½ centimeter at birth.

When Do Fontanelles Close?

The skull bones do not completely close during childhood because the brain still needs room to grow. However, once the bones grow to the point that they fill in the open spaces, the fontanelles are considered closed.

Fontanelles close in this order: 

  • Posterior: Between 1 and 2 months
  • Anterior: Between 9 and 18 months 

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

Caring For Your Baby's Fontanelles

While caring for your baby’s fontanelles is not complicated, it does involve understanding what’s normal and knowing what to watch for. Here are some of the things you should know. 

  • Your baby’s fontanelles should look flat against their head. They should not look swollen and bulging or sunken 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 anterior fontanelle may look raised or like it’s bulging. As long as it goes back to normal once the baby is upright and calm, there is no cause for concern. 
  • You may notice that the fontanelle seems to be pulsating in rhythm with your baby's heartbeat. This is also completely normal. 

Although the soft spot is a space between the skull bones, a tough membrane over the opening protects the soft tissue and the brain inside. So you can:

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

As with all other aspects of caring for your infant, always make sure to handle your baby gently. With practice, you'll develop more confidence. As long as you do not put pressure on your baby's soft spot, you don't need to worry that you're hurting them.

Soft Spot Concerns

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

Sunken

It is normal for the fontanelle to have a slight inward curve. However, a fontanelle that sinks down into your baby’s head could be a sign of dehydration, which happens when they aren't drinking enough fluids or are losing more fluids than they're taking in.

Your child can become dehydrated if they: 

Other signs of dehydration include not producing enough urine, excessive sleepiness, irritability, dry mouth, and crying without tears.

Dehydration in newborns and young children is considered a medical emergency. If your child is showing signs of dehydration and/or you notice that their fontanelles are sunken, call your pediatrician right away.

Bulging

As mentioned above, it is normal for a baby's fontanelle to be slightly raised when they are crying or vomiting. Both of these actions briefly increase the pressure inside the skull.

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 problem.

A bulging fontanelle could mean there is a buildup of fluid or swelling in the brain. These are dangerous conditions that require immediate medical treatment.

If you notice that your baby's soft spot feels hard or is bulging, call your pediatrician.

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 (a condition caused by vitamin D deficiency).

If you are concerned that your baby's soft spot has not closed after about 1 year of age, talk to your pediatrician.

Your pediatrician will be monitoring your baby's fontanelles in every checkup from birth until they are closed. If you are worried about their size or appearance, be sure to voice your concerns.

Closes Too Soon

It is possible, although rare, for the fontanelles to close too early. Sometimes the soft spots cannot be felt easily and may seem closed, but they are still open.

Premature fusing of the skull bones is a condition called craniosynostosis. Both the brain’s growth and the shape of the baby’s head can be affected by this condition.

Another result of the skull bones fusing too soon can be pressure building up inside the baby’s skull. While the Centers for Disease Control and Prevention (CDC) report that very mild cases of craniosynostosis may not need treatment, in many cases surgery is required to relieve the pressure and allow the brain to grow normally.

Head Shape

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

Molded Head

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.

Especially if you had a long or difficult vaginal delivery, your baby's head may appear cone-shaped or even pointy. Within a few days, though, it will 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.

If your baby lies on their back to sleep and sits in a car seat for long stretches of time while awake, the back of their head can become flat, a condition known as positional plagiocephaly.

The “back to sleep” campaign is important and works to lower the risk of sudden infant death syndrome (SIDS). However, it can increase the chances of plagiocephaly.

To prevent prolonged pressure on one area of your baby's head, change their position frequently during the day. Place your child on their back to sleep, but then give the back of their head a rest when they're awake.

You can try some of these positions to provide relief for the back of your child's head:

  • Carry your baby in your arms
  • Use an infant sling
  • Let them spend time on their tummy
  • Give them things to look at that will turn their head from side to side when they're on their 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 also 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 fontanelles are there and what they should look like can help you feel more confident as you care for your child. If you are worried or have any questions about your baby’s fontanelles, talk to your pediatrician. 

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Article Sources
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