Sunken Fontanelles
A sunken fontanelle occurs when a baby's "soft spot," which provide the skull with the flexibility needed to pass through the birth canal and a...

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What Are Sunken Fontanelles?

A baby is born with several fontanelles. These are more commonly known as soft spots. They provide the skull with the flexibility needed to pass through the birth canal. This flexibility also allows the baby’s brain and skull to grow during the first year of life. In newborns, soft spots are found on the top, back, and sides of the head.

The number of soft spots on an infant’s head depends on his or her age. According to the National Institutes of Health, the one on the back of the head disappears by one to two months of age. The one on the top of the head, on the other hand, remains until the baby is between 7 and 19 months old (NIH, 2011).

A baby’s soft spots should be relatively firm and ever so slightly curved inward. A soft spot with a noticeable inward curve is known as a sunken fontanelle.

This condition requires immediate medical attention but is usually easy to treat.

Common Causes of a Sunken Fontanelle


According to a 2003 journal article in American Family Physician,the most common cause of a sunken fontanelle is dehydration (Kiesler and Ricer, 2003). This condition occurs when there is a shortage of water and other essential fluids in the body.

According to the NIH infants are at an increased risk of becoming dehydrated compared to adults. There are two reasons: Infants’ body mass is smaller, and they process water and essential electrolytes at a faster pace (NIH, 2011).

A sunken fontanelle is one of several characteristic symptoms of infant dehydration. Others include decreased urine output (or an absence of urine output in severe cases), urine that is dark yellow in color, sunken eyes, and lack of energy.

Reporting any of these additional symptoms may help in the diagnostic process.


A second explanation for the condition is malnutrition. This occurs when infants are not getting all the nutrients they need for good health. However, this is a less likely cause, especially in the developed world.

When to Seek Medical Attention for a Sunken Fontanelle

If your child or another infant has a sunken fontanelle, you should seek medical attention as soon as possible. This is not a symptom you should try to treat at home.

How a Sunken Fontanelle Is Typically Diagnosed and Treated

When a medical professional examines a baby with a sunken fontanelle, the doctor will likely complete the following steps:

First, he or she will do a physical examination that will include looking at and feeling the affected area. The doctor will also likely assess the skin’s elasticity (“turgor”). Poor elasticity can also be a sign of low fluid levels. The amount of moisture in the eyes and mouth can also provide clues about the baby’s level of hydration.

Second, the doctor will ask you about the baby’s symptoms. It is important to provide as much information as possible. The doctor will likely want to know:

  • when the problem appeared
  • how you would rank the severity of the symptom considering the normal appearance of the infant’s soft spots
  • whether the baby has been sick recently
  • if the baby recently had any bouts of vomiting or diarrhea
  • if there was a recent period during which the baby perspired more than usual
  • if the baby seems thirsty
  • whether the baby’s level of alertness seems normal

The doctor may then order one or more tests. These might involve taking a blood or urine sample. Specific tests may include:

  • complete blood count (CBC): This blood test measures the number of red and white blood cells as well as their components to detect dehydration.
  • urinalysis: This analysis involves a number of tests to check urine for abnormalities that might indicate dehydration.
  • comprehensive metabolic panel: This blood analysis involves a number of tests to assess how well various chemicals in the body are breaking down and using food. It can help detect malnutrition.

Finally, if dehydration is the confirmed cause, the baby will be given fluids through an intravenous (IV) line inserted into his or her arm. This will likely bring fluid levels in the body back up to where they should be. If malnutrition is the cause, the baby will likely receive IV nutrients as well as fluids.

How to Prevent a Sunken Fontanelle

The best way to prevent a sunken fontanelle is to prevent dehydration, the most common cause. Some tips to prevent dehydration include:

  • giving the child adequate amounts of fluids
  • seeking medical help if you have a sick infant you believe is in danger of becoming dehydrated
  • increasing the amount of fluids given as soon as a baby vomits or has diarrhea

Check with your child’s doctor if you have questions about breastfeeding or how much formula to give your infant.

Written by: Krista O'Connell
Edited by:
Medically Reviewed by: George Krucik, MD
Published: Jul 5, 2012
Published By: Healthline Networks, Inc.
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