Fontanelle — Explained by Medical Evidence, Not Myths

A fontanelle is the soft, membrane-covered space between the bones of a baby's skull. It is a normal part of infant development that allows the head to adapt during birth and gives the brain room to grow, although certain changes in its appearance can signal a need for medical advice.

What a fontanelle is

The fontanelle is the soft area where the bones of a baby’s skull have not yet fully joined together. These spaces are covered by a tough membrane, so although they feel softer than bone, they are not an unprotected opening. In everyday language, people often call the fontanelle the “soft spot.”

This feature is normal and expected in infants. It helps the baby’s head change shape slightly during birth and, just as importantly, allows the brain and skull to grow rapidly during the first months and years of life. As the child develops, the skull bones gradually move closer together and the fontanelles close.

Most parents notice the larger front fontanelle on the top of the head. There is also a smaller one toward the back of the head. Several smaller sutures and spaces are also present in newborn skulls, but the main fontanelles are the ones most often discussed during checkups.

Why babies have soft spots

The infant skull is made of several separate bones rather than a single solid structure. Between these bones are fibrous joints called sutures, along with wider soft areas called fontanelles. This design is a healthy adaptation, not a weakness.

During labor and delivery, the flexibility of the skull can help the head pass through the birth canal. After birth, the same flexibility supports rapid brain growth. A baby’s brain grows quickly in the first two years of life, and the skull needs room to expand.

Because of this normal anatomy, the shape of a newborn’s head may look a little molded or uneven at first. In many babies, this improves over time. Doctors assess head shape, head growth, and the fontanelle together during routine well-baby visits.

If there are concerns about abnormal skull development, a pediatric specialist may look for conditions such as craniosynostosis, in which one or more skull sutures close too early.

Normal size, feel, and timing of closure

The largest fontanelle is the anterior fontanelle, located near the top front of the head. It is usually diamond-shaped and can vary in size from one baby to another. The posterior fontanelle, located toward the back of the head, is smaller and often closes earlier.

Closure timing is not identical for every child. In general, the posterior fontanelle closes within the first months of life, while the anterior fontanelle often remains open into the second year. A pediatrician looks at the pattern over time rather than relying on one single measurement.

It is also normal for the fontanelle to move slightly. Parents may notice gentle pulsations that reflect the baby’s heartbeat, especially when the baby is calm. A soft spot may also appear a little more sunken when a baby is upright and a little fuller when lying down, which can be normal.

What matters most is the overall picture: feeding, hydration, growth, behavior, and development. A normal fontanelle is usually soft and flat or slightly curved inward, not tense or dramatically depressed.

Changes that may need attention

A fontanelle that looks markedly sunken can sometimes suggest dehydration, especially if the baby is also feeding poorly, making fewer wet diapers, or seems unusually sleepy. Vomiting, diarrhea, fever, or difficulty feeding can contribute to fluid loss in infants, so a sunken soft spot should be considered alongside other symptoms.

A bulging fontanelle can happen briefly when a baby cries, coughs, vomits, or lies flat, and this may be harmless if it settles quickly. However, a fontanelle that stays tense or bulging when the baby is calm and upright can point to increased pressure inside the skull and needs prompt medical assessment.

Early closure is not always a problem, but if the skull shape is unusual or head growth seems restricted, doctors may check for premature fusion of the sutures. Delayed closure may also be normal in some children, but sometimes it is associated with conditions that affect growth, bone development, or thyroid function.

The key point is that the fontanelle alone rarely provides the whole answer. Doctors interpret it in the context of head circumference, physical examination, developmental progress, and, when needed, imaging or lab tests.

What can affect the fontanelle

Several normal and medical factors can influence how a fontanelle looks or feels. A baby’s position, crying, straining, and hydration status can all make temporary differences. This is why doctors prefer to examine the fontanelle when the infant is calm.

Medical causes of an abnormal-appearing fontanelle may include dehydration, infection, bleeding, problems affecting brain fluid pressure, nutritional issues, or disorders of bone and hormone regulation. In some cases, an unusually shaped head or concerning closure pattern leads to further evaluation.

Doctors may also think about conditions such as hydrocephalus if there are signs of increased head size, vomiting, irritability, or a persistently tense soft spot. The concern is not based on appearance alone but on the complete clinical picture.

• Temporary fullness can occur with crying or lying down.
• Sunken appearance may be linked to dehydration or poor intake.
• Persistent bulging may require urgent evaluation.
• Early or late closure may prompt assessment of skull growth and development.

How doctors evaluate fontanelle concerns

Evaluation usually begins with a detailed history and physical examination. The doctor asks about feeding, wet diapers, fever, vomiting, growth, behavior, birth history, and developmental milestones. They also examine the shape of the skull, measure head circumference, and assess the baby for signs of illness or dehydration.

In many cases, no testing is needed because the fontanelle is normal for the child’s age and condition. If there is concern, the next steps depend on the suspected cause. Blood tests may be used when dehydration, infection, or metabolic issues are possible.

Imaging may be recommended in selected situations. In infants with open fontanelles, a cranial ultrasound can sometimes provide useful information without radiation. Other cases may require MRI or CT scan to evaluate the skull, brain structures, or pressure-related concerns more closely.

If the problem seems related to the shape of the skull or early suture closure, referral to pediatric neurosurgery, pediatrics, or craniofacial specialists may be advised. The goal is to identify significant conditions early while avoiding unnecessary testing when the findings are within normal limits.

Treatment and everyday care

Treatment depends entirely on the cause. A normal fontanelle does not need any treatment. Parents can gently wash and touch the scalp as usual; the membrane over the soft spot is durable enough for normal handling, cuddling, and hair care.

If dehydration is the issue, care focuses on restoring fluids and addressing the reason for poor intake or fluid loss. If infection, raised intracranial pressure, or a structural skull problem is suspected, treatment is directed at that underlying condition and may involve pediatric specialists.

When early suture fusion is confirmed, management may include close monitoring or pediatric neurosurgery depending on the severity and the child’s growth. If the concern relates to brain or nerve function, assessment by neurology specialists may also be part of care.

Near the end of the care pathway, families may benefit from coordinated follow-up. At Acibadem International, multidisciplinary specialists in JCI-accredited hospitals evaluate and treat infants with skull, neurological, and developmental concerns for international patients when such expertise is needed.

When to seek medical care

Parents should seek medical advice if the fontanelle seems persistently bulging, clearly sunken, or associated with symptoms such as fever, repeated vomiting, poor feeding, unusual sleepiness, irritability, seizures, or fewer wet diapers. These signs do not always mean a serious problem, but they should not be ignored in a young infant.

Urgent assessment is especially important if a bulging soft spot appears when the baby is calm, if the baby has a high fever, or if there is concern after a head injury. It is also reasonable to ask a doctor about a fontanelle that seems to close very early, remains open much longer than expected, or comes with an unusual head shape or slow head growth.

Routine well-baby visits remain one of the best ways to monitor fontanelle development. Pediatricians track head circumference, skull shape, and milestones over time, which helps distinguish normal variation from conditions that need further evaluation.

Frequently asked questions

Is the fontanelle supposed to feel soft?

Yes. The fontanelle normally feels softer than the surrounding skull because the bones have not fully joined yet. It is covered by a strong membrane, so gentle everyday touching, washing, and brushing are usually safe.

Can a fontanelle pulse?

Yes, a faint pulsing movement can be normal. It often reflects the baby's heartbeat and may be easier to notice when the baby is calm and the light is good.

When does the fontanelle close?

The smaller posterior fontanelle usually closes earlier, often within the first months of life. The larger anterior fontanelle commonly stays open longer and may close anytime during the second year, with some normal variation.

What does a sunken fontanelle mean?

A sunken fontanelle can sometimes be a sign of dehydration, especially if the baby is feeding poorly or making fewer wet diapers. It should be assessed together with the child's overall condition, because a mild dip can sometimes be normal depending on posture and hydration.

What does a bulging fontanelle mean?

A fontanelle may briefly look fuller when a baby cries, coughs, or lies down, and that can be normal. A fontanelle that stays tense or bulging when the baby is calm needs prompt medical evaluation because it can be linked to increased pressure inside the skull.

Should parents protect the fontanelle from normal handling?

Normal handling is usually fine. Parents do not need to avoid touching or washing the area, but they should always handle infants gently and support the head and neck as usual.

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.