O/T average head size of a 2 yr old???

I don't know the average, but my Spencer's head has always been 15th percentile or lower. At his last appointment it was no longer on the charts. Our pediatrician is sending us to a developmental / gentics doctor. Of course it takes forever to get in so our appointment is in November... Hnag in there and QUIT LOOKING ON THE NET! I freak myself completely out every time I try to self diagnose!