My ds is nearly 3.5 (on May 20th, he is 4 in Nov) and is only 90cm tall. He seems to have only grown 2cm since September (though it's difficult to know if we measured accurately then) although his feet have got bigger and he has moved from 2-3 tops into age 3 tops. He wears trousers for 18-24 month olds. His development seems fine in all other respects. We are both smallish but both the grandfathers are over 6 feet tall. Should I be concerned?