Sunken Fontanelle

by Dr. Pamela Bandelaria, pediatrician

Your baby’s body is constantly growing and changing, and as they grow some structures will change or disappear completely. There are a few body parts that are only present in the first few months of their life. One of these structures is the fontanelle.

This article will outline what the fontanelles are, why they are present and when they go away.  

What should the fontanelle feel like?

Fontanelles are also called soft spots on the baby’s head. A fontanelle will feel firm but pliable. It is sometimes flat, but it is also normal for the fontanelle to be slightly concave. A pulse can also be felt if slight pressure is applied to the fontanelle. This is because of the blood flow in your baby’s head. This pulsation is consistent with your baby’s heartbeat and is not usually a cause for concern.

The look and feel of the fontanelles can tell you a lot about your baby's condition. There are different medical conditions associated with abnormal fontanelles. Delayed closure of the fontanelle, or a bulging or sunken fontanelle can give you important clues about your baby's health and must be investigated. Physicians can do a thorough examination to help to identify if there is a problem with your baby.

Can you hurt a baby by pushing on their soft spot?

A slight touch on the soft spot usually does not hurt the baby. Touching and slightly pushing on the soft spot is part of a doctor’s physical examination to check if your baby has any health concerns that warrant investigation. In the same way, you can touch your baby's soft spots when handling and taking care of your baby. For example, when you are washing and bathing your baby, combing his hair, or dressing him in accessories (cap, headbands for girls, bonnets, etc.). Touching the soft spot is not usually a problem as long as it is done gently.

Why is my baby's head dented?

It is usual for the fontanelle to be slightly depressed, making it appear that your baby's head is dented. Sometimes the dents can also be caused by the movement of the skull bones as your baby passed through the birth canal. It is important to note that the fontanelle may have a slight curve inward because it is only covered by a membrane.  However, a very deep sunken fontanelle can indicate some serious medical conditions, such as dehydration. It is best to check for the fontanelle when the baby is in an upright position and when the baby is in a comfortable, relaxed state. When the baby is irritated or is crying, the fontanelle may bulge.  A bulging fontanelle is a warning sign that there is a problem in your baby's brain.  It is best to evaluate the fontanelle when the baby is asleep or feeding so that they are in a relaxed state.

How do you know if the fontanelle is sunken?

A sunken fontanelle is a visible and noticeable inward curve in the head which is a classic sign of dehydration. Your baby may not be receiving the proper amount of water that her body needs. The most common cause of dehydration in babies and children is diarrhea and vomiting. You will know that the fontanelle is sunken if the depression is prominent and deep. Another cause of a sunken fontanelle is malnutrition, though this is not as common as dehydration. Malnutrition is due to the lack of calories that the body needs for growth.

A slightly sunken fontanelle is a subjective finding. As previously mentioned, the fontanelle is normally slightly depressed. Still, if it is very prominent, or if other signs and symptoms accompany it, it is best to have your baby checked by a medical professional.  A thorough physical examination done by physicians can aid in knowing the problem of your baby and how best to manage it.

At what age does a baby's fontanelle close?

As the baby grows, the fontanelles close. The anterior fontanelles usually close at around 18 months on average, but some close as early as nine months. The posterior fontanelle closes after six to eight weeks. Fontanelles close as the sutures fuse and the cranial bones mature and turn into the hard, calcified, skeletal material that makes up the skull. The timing of the closure is important because delayed closure may be indicative of certain illnesses.              

When should I worry about a sunken fontanelle?

A sunken fontanelle is a cause for concern if it is very prominent and sunken. A sunken fontanelle is usually not an isolated finding, and there will be other signs and symptoms that accompany it. Signs of dehydration include:

• Sunken eyes

• Minimal or no tears

• Dry lips and membranes

• Irritability or decreased sensorium

• Pale and cool skin

• Decreased or no urine output

Malnutrition is also accompanied by other signs and symptoms such as failure of your child to grow, fatigue, dry skin, and brittle or dry hair. When these are present in your baby, it is best to bring them to the doctor.

How do I hydrate my newborn?

Dehydration occurs due to a lack of fluids. The use of an oral rehydrating solution is one of the ways to hydrate your baby. It contains electrolytes that are lost when your baby is vomiting or has diarrhea. For every bowel movement or vomit passed, you must give the rehydration solution to your baby in proportion to the amount lost. Oral rehydration at home can be done if your baby can tolerate food or drinks, or if your baby is not persistently vomiting. However, if the symptoms of dehydration persist or worsen, it warrants immediate hospital care in the form of a drip for faster correction of the dehydration. Dehydration can be life-threatening if it is managed too late, so it is important to know when you should bring your baby to the hospital.

Conclusion

A soft spot on your baby’s head is normal. It usually feels flat and soft, but may sometimes have a slightly concave appearance. Fontanelles are important landmarks and can provide clues about your baby’s health. You should watch out for signs of an abnormal fontanelle and immediately bring your baby for a medical evaluation. It is also important to know the signs of dehydration that accompany a sunken fontanelle. You can hydrate your baby at home if they have fluid losses, but take them to your doctor for thorough care if the condition persists or worsens.