does she have any teeth yet or not? that would give us a clue as to how old she is.
is she teething?
does she drool? does she cry all night long? does she chew on her fists? does she put everything into her mouth? she acts out her words.
or else you could weigh her; that would tell you how old she is.
or else her hair. does she have lots of hair?
gee, he's really something, your grandson -- is he good at math too?
this guy asked for advice, i'm giving him advice, okay? if you're so paranoid, why don't you run home and chain your kid to his crib?