Enlarged fontanelles are larger than expected soft spots 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 fontanelle (fontanel or fonticulus).
Soft spot - large
Fontanelles allows 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:
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.
What to expect at your health care provider's office
An enlarged large fontanelle is almost always found by the health care provider during a physical exam.
The health care provider will examine the child and measure the child's head around the largest area.
The doctor 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.
Cohen A. Disorders of the head shape and size. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin’s Neonatal-Perinatal Medicine. 9th ed. St. Louis, Mo: Mosby Elsevier; 2010:chap 40.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.