Fontanelles - enlarged

Soft spot - large; Newborn care - enlarged fontanelle; Neonatal care - enlarged fontanelle

Enlarged fontanelles are larger than expected soft spots in the head for the age of a baby.

The skull of an infant or young child is made up of bony plates that allow for growth of the skull. The borders at which these plates intersect are called sutures or suture lines. The spaces where these connect, but are not completely joined, are called soft spots or fontanelles (fontanel or fonticulus).

Considerations

Fontanelles allow for growth of the skull during an infant's first year. Slow or incomplete closure of the skull bones is most often the cause of a wide fontanelle.

Causes

Larger than normal fontanelles are most commonly caused by:

Down syndrome
Down syndrome
Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46.

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Hydrocephalus
Hydrocephalus
Hydrocephalus is a buildup of fluid inside the skull that leads to the brain pushing against the skull. Hydrocephalus means "water on the brain. "...
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Intrauterine growth retardation (IUGR)
Intrauterine growth retardation
Intrauterine growth restriction (IUGR) refers to the poor growth of a baby while in the mother's womb during pregnancy.
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Premature birth

Rarer causes include:

Achondroplasia
Achondroplasia
Achondroplasia is a disorder of bone growth that causes the most common type of dwarfism.

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Apert syndrome
Apert syndrome
Apert syndrome is a genetic condition in which the seams between the skull bones close earlier than normal. This affects the shape of the head and f...
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Cleidocranial dysostosis
Cleidocranial dysostosis
Cleidocranial dysostosis is a disorder involving the abnormal development of bones in the skull and collar (clavicle) area.

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Congenital rubella
Congenital rubella
Congenital rubella is a condition that occurs in an infant whose mother is infected with the virus that causes German measles. Congenital means the ...
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Neonatal hypothyroidism
Neonatal hypothyroidism
Neonatal hypothyroidism is decreased thyroid hormone production in a newborn. In very rare cases, no thyroid hormone is produced. The condition is ...

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Osteogenesis imperfecta
Osteogenesis imperfecta
Osteogenesis imperfecta (OI) is a condition causing extremely fragile bones.

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Rickets
Rickets
Rickets is a disorder that occurs in children before bone growth is complete. It is caused by a lack of vitamin D, calcium, or phosphate. It leads ...
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When to Contact a Medical Professional

If you think that the fontanelles on your baby's head are larger than they should be, talk to your child's health care provider. Most of the time, this sign will have been seen during the baby's first medical exam.

What to Expect at Your Office Visit

An enlarged large fontanelle is almost always found by the provider during a physical exam.

The provider will examine the child and measure the child's head around the largest area.
The provider may also turn off the lights and shine a bright light over the child's head.
Your baby's soft spot will be regularly checked at each well-child visit.

Blood tests and imaging tests of the head may be done.

Open References

References

James KC, Piña-Garza JE. Disorders of cranial volume and shape. In: James KC, Piña-Garza JE, eds. Fenichel's Clinical Pediatric Neurology. 9th ed. Philadelphia, PA: Elsevier; 2025:chap 18.

Trowbridge SK, Yang E, Yuskaitis CJ. Congenital anomalies of the central nervous system. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 631.

Skull of a newborn - illustration
The sutures or anatomical lines where the bony plates of the skull join together can be easily felt in the newborn infant. The diamond shaped space on the top of the skull and the smaller space further to the back are often referred to as the soft spot in young infants.
Skull of a newborn
illustration
Fontanelles - illustration
Fontanelles are the soft spots on an infant's head where the bony plates that make up the skull have not yet come together. It is normal for infants to have these soft spots, which can be seen and felt on the top and back of the head. Fontanelles that are abnormally large may indicate a medical condition.
Fontanelles
illustration
Large fontanelles (lateral view) - illustration
A wide fontanelle occurs when the fontanelle is larger in size than expected for the age of the baby. Slow or incomplete ossification of the skull bones is most often the cause of a wide fontanelle.
Large fontanelles (lateral view)
illustration
Large fontanelles - illustration
The bones of the skull are not joined together firmly at birth. The sutures gradually accumulate minerals and harden (this process is called ossification), firmly joining the skull bones together. In an infant, the spaces where sutures intersect but don't completely touch is called the soft spot, a membrane covered area also called a fontanelle (fontanel or fonticulus). The fontanelles allow for growth of the skull during an infant's first year. When the spaces of the fontanelles are larger than normal underlying causes such as hydrocephalus may be suspected.
Large fontanelles
illustration

Skull of a newborn - illustration
The sutures or anatomical lines where the bony plates of the skull join together can be easily felt in the newborn infant. The diamond shaped space on the top of the skull and the smaller space further to the back are often referred to as the soft spot in young infants.
Skull of a newborn
illustration
Fontanelles - illustration
Fontanelles are the soft spots on an infant's head where the bony plates that make up the skull have not yet come together. It is normal for infants to have these soft spots, which can be seen and felt on the top and back of the head. Fontanelles that are abnormally large may indicate a medical condition.
Fontanelles
illustration
Large fontanelles (lateral view) - illustration
A wide fontanelle occurs when the fontanelle is larger in size than expected for the age of the baby. Slow or incomplete ossification of the skull bones is most often the cause of a wide fontanelle.
Large fontanelles (lateral view)
illustration
Large fontanelles - illustration
The bones of the skull are not joined together firmly at birth. The sutures gradually accumulate minerals and harden (this process is called ossification), firmly joining the skull bones together. In an infant, the spaces where sutures intersect but don't completely touch is called the soft spot, a membrane covered area also called a fontanelle (fontanel or fonticulus). The fontanelles allow for growth of the skull during an infant's first year. When the spaces of the fontanelles are larger than normal underlying causes such as hydrocephalus may be suspected.
Large fontanelles
illustration

A Closer Look

Talking to your MD

Self Care

Tests for Fontanelles - enlarged

Review Date: 10/7/2025

Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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Health Library

Fontanelles - enlarged

Considerations

Causes

Down syndrome

Hydrocephalus

Intrauterine growth retardation

Achondroplasia

Apert syndrome

Cleidocranial dysostosis

Congenital rubella

Neonatal hypothyroidism

Osteogenesis imperfecta

Rickets

When to Contact a Medical Professional

What to Expect at Your Office Visit

References

Skull of a newborn - illustration

Skull of a newborn

Fontanelles - illustration

Fontanelles

Large fontanelles (lateral view) - illustration

Large fontanelles (lateral view)

Large fontanelles - illustration

Large fontanelles