Baby Got a Sunken Fontanelle? Know the Causes and Treatments

Some parents will become concerned when they notice their baby has a sunken fontanelle. The fontanelle is the baby’s “soft spot” where the skull bones have not yet closed. In newborns, the bones of the skull are separate from each other in order to allow the baby to be born. They also remain separate to give the baby’s brain room for rapid growth in the first few months.

You will notice during well-baby checks the doctor checks the baby’s fontanelle. This is because they want to make sure the skull is not closing up too quickly. They are also looking for a fontanelle that is sunken in, because this can be a sign of trouble. 

What Causes Sunken Fontanelle in Baby?

1.    Dehydration

Dehydration is one of the major causes. It is important to understand that babies are at much higher risk of dehydration than adults due to their small size. They also tend to go through water faster than adults. If a baby becomes ill or has feeding issues, dehydration can set in very quickly. Here are the signs of dehydration in babies:

  • Depressed fontanelle
  • Mucous membranes, lips and skin are dry
  • Less wet diapers than normal
  • Eyes appear sunken
  • Strong and dark urine
  • No tears when crying
  • Lethargic and sleepy
  • Fast or labored breathing
  • Extremities are mottled and cool to the touch

2.    Malnutrition

A less daunting name for this is “Failure to Thrive” in infants-- a common condition when a baby has absorption issues and cannot properly absorb nutrients. It may also be caused by feeding problems, food intolerances, or genetic conditions. In third world countries, it could just be lack of formula or breast milk.

At each check-up, your pediatrician will check the baby’s soft spot. If there's anything to worry about, the doctor will assess feeding concerns further.

How Is Sunken Fontanelle in Baby Diagnosed?

When your new baby goes in for each check-up the doctor will check the fontanelle’s to make sure they are okay. You want them to be open, but not sunken in. If you notice at home that your baby’s fontanelle’s are sunken, you need to contact the doctor. At the visit they will do the following:

1.  Do an Examination

Your baby’s doctor will check over his or her entire body. They will feel the fontanelle’s to check if they are truly sunken in. They will look at the skin to see if it snaps back when pinched. They also look at the eyes and mouth to see if they are dry. This can all tell you if the baby is hydrated enough.

2.  Ask You About How Baby Is Doing

The doctor may ask how baby is acting and feeding. Be prepared to tell the doctor the following:

  • If the baby is alert when he or she is awake or if they are overly sleepy
  • How long you have noticed the sunken fontanelle
  • If you think there has been a significant change in how baby is acting
  • If your baby is very thirsty
  • Any recent illness in baby or in the household
  • Has your baby had diarrhea or vomiting
  • Has your baby been sweating more than usual? Is it hot in your house?

3.  Lab Tests May Be Ordered If Needed

If the doctor thinks there is a problem, he may order lab testing. These may include:

  • Complete Blood Count (CBC). It tests for infection, anemia and if the body is dehydrated.
  • Urine. Urine can show dehydration. There are a number of indicators in a urinalysis. It can also check for urinary tract infection, which can disrupt the fluid balance.
  • Comprehensive Metabolic Panel (CMP). This can tell the doctor how the different organs are working. It can also show dehydration and if your baby is suffering from malnourishment.

How Is Sunken Fontanelle in Baby Treated?

If your baby’s doctor finds that your baby is dehydrated, they will most likely be put in the hospital on IV fluids via a needle in a vein. In very young babies, dehydration is a medical emergency and should not be treated at home. If your baby is suffering from malnutrition, they may start tube or intravenous feedings as well.If your doctor thinks your baby can be treated at home, here are some things they might suggest:

  • Give plenty of liquids. You will need to offer baby extra liquids. Breastfeed more often or offer more formula feedings. You can try small sips often instead of full feedings. Do not dilute the formula. If your baby is already on solid foods, you can offer bottles of water or a pediatric electrolyte replacement drink. Do not give your baby soda or fruit juice.
  • Use a pediatric electrolyte replacement. Keep a bottle made up of electrolyte replacement. Use only approved types and not sports drinks. These help replace potassium, sugar and salt in your baby’s body.
  • Try an over-the counter pain reliever. When babies don’t feel well or have a sore throat, they tend to refuse feedings. Your doctor may recommend trying an over-the-counter infant pain reliever. Acetaminophen is only recommended for babies two months of age or older and Ibuprofen is only recommended for babies three months of age or older. If you are unsure of dosage, make sure you get the correct amount from a doctor or pharmacist.
  • Keep baby cool on hot days. If the weather is hot and your baby is dehydrated, keep them cool, away from the sun and out of the heat. Give extra fluids on hot days i.e. water bottles for babies on formula and solids, breastfeed more often for breastfed babies).

How to Prevent Sunken Fontanelle in Baby

Preventing your baby from getting dehydrated helps prevent a sunken fontanelle. If your baby is not eating or drinking well, make sure you offer fluids often. Make sure you feed your baby whenever they are hungry, which is called “on-demand feeding.” If your baby gets sick, feed them small sips of fluids often. If your baby is suffering from malnutrition, make sure you are clear about how much they should be eating for their age and weight. This feeding chart for babies up to 1 year old can help.