At my son's last check-up the doctor indicated that his head circumference was in the 95th percentile. At three months of age he had the head of a five-month-old. Is there a chart that I could refer to that shows head circumference percentiles? I would like to be able to track his measurements in order to monitor whether we need to be concerned about fluid in his head.
The most important question is whether your son has always had a large head, or whether it is getting disproportionately larger over time. It should get measured at every well-child check-up. In general, a stable, large head, especially if one or both parents have large heads, is less worrisome than one that keeps expanding.
For your reference, check out the CDC's growthcharts online. This is the site of the government agency that creates the charts used by pediatricians. They can be viewed and downloaded from this site.