Baby in 90th percentile

Had my 20 week ultrasound 2 weeks ago and baby boy was measuring 1 week and 1 day ahead and in the 90 percentile. 
Doctor said he's healthy and so am I that he will just keep track of how I measure. 
He's already planning another ultrasound later on to see how big he is because he said I more than likely will go early. 
Anyone else had a similar situation? Is it bad he is growing so big so fast?