Infant Head Size and Autism: Any link?

Q) Dear Dr. Gwenn:

My grandson recently had his 9 months check up. At birth and 3rd month check up his head size was in the 55% range. His weight and height wereclose to the 90%.At the latest 9 months checkup, his head size was in the 90th% and his weight and height were lower than the earlier months, more like 75th percentile. His developmental milestones have been very normal or above. He’s smiley, happy, eye contact, verbal–lots of sounds including mama and dadada—. He crawls everywhere and up on everything. First child for my son and daughter.