How do these percentiles make sense?

Question

I took my son to the doctor today. he measures way off the scale for height and weight, yet his head circumference is only 75%. I asked her if that means his head is too small for his body, and she said no its not. My son is very proportionate, so would he have to look like an alien to have balanced percentiles? He's 15mths old and has been walking on his own for a month now. what do these percentiles mean, and how are they significant? and how old is a child before this scale for measurement isn't used anymore.

Answer 1

Don't read too much into the percentiles.  What 75% means is that his head circumference is the same size as 75% of the children his age.  It's nothing to worry about.  

I think they can use that measurement scale all the way through childhood.