Clothes sizes

Anne 💙💙💙 • Mom to 3 boys. August 2015, December 2016, December 2018
Why do they do baby clothes sizes by month? Because that is not the size they are when they are in that. My son is 4 months and almost out of 6 month clothes. It's hard to plan ahead! Does the growing ever slow down? He has quadrupled his weight since birth. Started at just under 4lbs and now he is almost 16!