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Newborn and Infant Care

Large head circumference, almost closed



Hi, My four month old son has a head size of 42.5, weighs 6.100 kilo, and is 62 long . His anterior fontanelle is almost closed. The doctor raised concern about his head size and said we would need to check it in a month again. if it grows too much he would send me for a CT. what do you think about his head size and the fact that his fontanelle is almost closed at four months instead of 9-18 months

thank you so much for your help


I am sure that had to be really scary news! On the good side, your son's doctor is doing the right thing in terms of careful monitoring and recognizing that there may be a problem. On the other side, closure of the anterior fontanelle occurs in 1% of babies, most of them boys, and is a normal genetic variant. It is worthwhile to ask your mother and the baby's father's mother if either of you had early closure of the fontenelle.

I plotted your son's measurements and found that he is at about the 25th percentile for his length and weight, which means he is a healthy weight for his length. It also means that he weighs more and is longer than 25% of little 4-month-old boys, but 75% are larger. His head circumference, if it was accurately measured, falls between the 50th and 75th percentiles. So it is larger compared to his length and weight. However, if you are breastfeeding, it is common for breastfed babies to be leaner than bottle fed babies. It is also not unusual for there to be a mismatch in growth percentiles of this nature. Also, if you or your husband tend to have larger heads than average, as judged for adults by hat size, your son may simply be reflecting his genetic heritage.

Between large head size and early fontanelle closure, the more worrisome is really the early fontanelle closure, which may be entirely normal. There is a condition called craniosynostosis in which the cranial bones fuse together too early to accommodate the rapid brain growth of the first two years of life, precluding as well the additional 25% growth that occurs up until the second decade of life when the bones normally fuse. One of the hallmarks of this condition is early fontanelle closure. It can be treated surgically very successfully. There are a number of other conditions that are associated with early fontanelle closure but these are the two most likely - normal variation and craniosynostosis.

Your son's pediatrician is following the very best course of action, which is to monitor his head growth and obtain a CT scan to identify any problems or to confirm that your son is absolutely normal, just an early fontanelle closer. In the meantime, you might want to check with your son's grandparents about his parents' head growth as babies and to get your hat size and his father's hat size as additional information for your next doctor visit. Also be sure to provide supervised tummy time for your son to prevent a mis-shapen head that can cause concern when none is necessary. Tummy time is great for building head control and strengthening neck and should muscles to help babies sit and crawl. If your son does not enjoy it, start with just 5 minutes and lay down on the floor to play with him and make it a fun time, gradually increasing tummy time to several periods each day.

I hope this is helpful information.

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Response by:

Mary M Gottesman, PhD, RN, CPNP, FAAN Mary M Gottesman, PhD, RN, CPNP, FAAN
Professor of Clinical Nursing
College of Nursing
The Ohio State University