A bulging fontanel (or fontanelle) is a medical emergency. Parents or caregivers should call a pediatrician or take the baby to the emergency room immediately if they notice a bulging soft spot.

Sometimes, the fontanel bulges for harmless or temporary reasons, but it is important for a doctor to examine the baby immediately to rule out potentially life threatening issues, such as meningitis.

Babies are born with six fontanels, which people commonly refer to as soft spots. The most noticeable are the anterior and posterior fontanels, which are, respectively, on top of the head toward the front and at the back of the skull.

In this article, we look at the causes of a bulging fontanel, when to seek help, and what to expect at the hospital. We also explain how to prevent a bulging fontanel and what can happen if a baby with this issue does not receive care.

a baby with a bulging fontanelle lies asleep in a cribShare on Pinterest
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A bulging fontanel means that the soft spot looks bigger than usual.

The normally soft area may swell up taller than the rest of the skull.

The baby’s head may appear to change shape, or the soft spot might look misshapen. Sometimes, the baby’s whole head looks bigger.

Parents and caregivers can better detect a bulging fontanel if they know how the baby’s head usually looks. Therefore, it is advisable to pay close attention to the baby’s skull so that it is possible to detect any changes.

A bulging fontanel has many possible causes, which vary in severity. We explore some of these in more detail below.


A bulging fontanel often indicates that the baby has hydrocephalus.

Hydrocephalus causes fluid accumulation in the brain’s ventricles, which are spaces containing cerebrospinal fluid.

The pressure of the fluid widens the ventricles, potentially placing pressure on the brain tissue and causing the fontanel to swell.

There are many possible causes of hydrocephalus. Sometimes, it is present at birth, in which case, doctors call it congenital hydrocephalus. When people develop the condition after birth, it is called acquired hydrocephalus.

Congenital hydrocephalus

Some risk factors for hydrocephalus and a bulging fontanel at birth include:

  • Infection: Certain infections, such as rubella, can transmit from a pregnant person to the baby, potentially causing brain swelling.
  • Brain bleeding: This issue is more common in premature babies and those who sustain injuries or experience oxygen deprivation during the birth.
  • Birth abnormalities: Abnormalities that affect the development of the brain, skull, spinal cord, or other parts of the nervous system can increase the risk of congenital hydrocephalus.

Acquired hydrocephalus

Some babies suddenly develop a bulging fontanel after birth. The possible causes of this medical emergency include:

  • Infections: An infection in the brain or spinal cord, such as bacterial meningitis, may cause a bulging fontanel. This is more likely when the baby has a fever.
  • Injuries: Brain and spinal cord injuries, including blows to the head, may cause swelling in the brain.
  • Tumors: Tumors in the brain or spinal cord may cause hydrocephalus.
  • Stroke: A stroke is very rare in babies but is still possible.

Other causes

Hydrocephalus does not cause all bulging fontanels. Some other potential causes include:

  • Transient intracranial hypertension: This condition happens when a baby temporarily develops high blood pressure in the brain, causing it to swell. It sometimes follows an infection. While the condition usually goes away on its own, it is still a medical emergency and is not possible to diagnose from home.
  • Crying: Sometimes, crying creates temporary pressure in the brain from cerebrospinal fluid. In these cases, the bulge usually goes away on its own. However, babies may cry a lot when they have a serious illness, so it is not safe to assume that crying is the direct cause of a bulging fontanel.
  • Vomiting: Similar to crying, vomiting can create pressure in the skull. Vomiting may also occur with life threatening illnesses, so vomiting with a bulging fontanel is still an emergency.
  • Vaccinations: Babies occasionally develop a benign and temporary bulging fontanel following vaccinations. The exact reason for this is unknown, but researchers believe that it is related to the fever that vaccinations can cause as a side effect.
  • Drugs and nutrition: Certain nutritional issues, such as vitamin deficiencies, may cause the fontanel to bulge. Some drugs may also cause a bulging fontanel.
  • Body position: If a baby is lying down, their fontanel may appear swollen. If the fontanel does not swell in an upright position, there is likely not a problem.

Parents and caregivers should always seek immediate medical help for a bulging fontanel, even if they suspect that the cause is something harmless.

It is important not to assume that crying or vomiting caused the swelling. It is just as likely that an infection or trauma caused the crying or vomiting, as well as the swelling.

Anyone who notices a bulging fontanel on their baby should take them to the hospital or call 911.

A bulging fontanel often signals a serious medical condition.

It may mean that there is fluid on or around the brain. This fluid can damage brain tissue, causing severe disabilities.

The cause may be a serious infection or other injury, which could be fatal.

It can be scary to see a bulging fontanel, and parents or caregivers may worry about painful or invasive treatments. However, the faster the baby gets treatment, the better their outlook.

Even in the case of a very serious infection, prompt treatment can help the baby feel better very quickly. Delaying care can cause permanent health issues.

Doctors will work as quickly as possible to determine the cause of the bulging fontanel.

They may ask questions about the baby’s development, daily routine, and medical history, including whether they have recently been ill.

In addition, doctors will take the baby’s temperature and do blood work. They may also take scans of the brain.

In many hospitals, doctors routinely perform a lumbar puncture, which some people call a spinal tap.

A lumbar puncture involves inserting a needle into the area around the spine to get a sample of cerebrospinal fluid. While the procedure is generally safe and the most accurate way to determine whether an infection is causing the bulging fontanel, it can be stressful.

However, a 2008 study suggests that this might not be necessary if the baby seems healthy.

If a doctor suggests delaying a lumbar puncture, the hospital may admit the baby for monitoring.

If a lumbar puncture shows that there is no infection, and a doctor cannot identify the cause, the hospital may also recommend admitting the baby for monitoring.

The treatment will depend on the cause. If the baby has bacterial meningitis, they will need antibiotics.

Some forms of congenital hydrocephalus require ongoing support and care, such as physical and occupational therapy.

Babies with a head or spinal cord injury may also require ongoing care.

It is not always possible to prevent a bulging fontanel.

Some strategies that parents and caregivers can use to reduce the risk include:

  • washing the hands regularly and keeping a distance from people who are sick
  • getting regular checkups when pregnant to reduce the risk of infections, premature birth, and some birth abnormalities
  • protecting the baby from head injuries by buckling them securely into the right size and type of car seat, never leaving them unattended on a bed, counter, or couch they could roll off, and never taking them on a bike without a helmet
  • talking with a pediatrician about a healthful diet for the infant and adhering to the recommended well-baby visit and vaccination schedules
  • seeking immediate care for any unusual symptoms in a baby or young child

A bulging fontanel on a baby may be a sign of a serious problem that requires urgent treatment.

Although some relatively harmless conditions may also cause the swelling, it is impossible to determine the cause just from the symptoms, so it is crucial to seek medical care immediately.