my 3 month old son is 11.1 it really just depends on the baby. my son still wears newborn pants because other sizes don't fit but newborn pants are also too short on him haha. fit in the waste but not the legs.
My 2 month old is 11.10 so I think it just depends on the baby. Doc said my son is a little below average cause I switched him to formula
My friend gave birth to a 10 pounder Twice. Lol her babies are perfectly healthy. All babies are different. My son is 4 months and hes 13 pounds.