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).

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

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.

Larger than normal fontanelles are most commonly caused by:

• Down syndrome
• Hydrocephalus
• Intrauterine growth retardation (IUGR)
• Premature birth

Rarer causes:

• Achondroplasia
• Apert syndrome
• Cleidocranial dysostosis
• Congenital rubella
• Neonatal hypothyroidism
• Osteogenesis imperfecta
• Rickets

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

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.

Kinsman SL, Johnston MV. Congenital anomalies of the central nervous system. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 609.

Piña-Garza JE, James KC. Disorders of cranial volume and shape. In: Piña-Garza JE, James KC, eds. Fenichel's Clinical Pediatric Neurology. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 18.