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Home › Expert Q&A › Behavior and Development › When will my daughter's soft spot close?

Expert Q&A

 

By David L. Fay, M.D.
Family Physician
Associate Director, Waukesha Family Practice Residency Program

I have a 15 month-old twin girl, who still has her soft spot (fontanel). My pediatrician says she could have this until she's 2 years old. I have great concerns.

There are actually six fontanels (soft spots) when infants are born: the anterior (front) and posterior (back) are the easiest to feel and identify, since they are on the top of the head. There are also four smaller and less important fontanels, two on each side of the head. The anterior fontanel is the largest and is a diamond-shaped structure located just forward of the top of the head. The posterior fontanel is a triangular-shaped structure located at the "crown."

These fontanels are formed by fibrous tissue which loosely connects the seven skull plates. It is important at this stage of life to have the skull plates formed, but not fully fused. The reason for the hard, bony skull plates is pretty obvious: protection for the brain. However, when the infant is passing through the birth canal, the skull needs to be able to conform to the contours of the canal. The result of this is the molding (conehead!) we see when infants are born vaginally. This molding resolves spontaneously within a few days. The second reason for not having the skull plates fused is brain growth. The skull plates grow along with the brain, and only fuse together when brain growth slows. This generally happens at about two years of age. The brain and skull continue to grow slowly until about 15-16 years old, but the majority of the growth has been accomplished by two years of age.

In the case of the two most obvious fontanels, the posterior (smaller) fontanel usually closes by about four months of age. The anterior fontanel may sometimes get larger for the first month or so, but generally will diminish in size after six months, and usually is no longer noticeable after 9-18 months. Note that it is still open for a few months after it is no longer noticeable.

There are some rare abnormal conditions which may result in a persistent open fontanel, but there are usually other signs such as an excessively large head or other noticeable abnormalities; almost never does an open anterior fontanel by itself mean something serious is wrong. An infant with a persistent fontanel should be checked by measuring head circumference regularly, as well as by monitoring development and growth in other areas. If these are normal, an open fontanel is generally not something to worry about. As always, one's physician is the best qualified to discuss specifics.

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