I've never really heard anyone refer to weeks past about 16....after that I always hear months. My guess would be that when theyre so young...knowing the exact age something is happening may be important. For example teething is normal at a certain age, after that point the teeth should be pulled.
As far as growing. Mine stopped at about 14 months. But ive heard everything from 10 months to a year and a half.
Hope that helps |