What size clothes is your 12 month old wearing?
It actually totally depends on teh brad these days.
Gap runs close to right with their shirts but pants we are still in 18 months.
Most other brands she is 12-18 month t-shirts, and 18month or 2T bottoms. We gave up on onesies long ago.
S is really tall (90% percentile for height) but not overly chunky and that is what fits her well.
most of DDs stuff is 18 months tho some 12months fits her but starting to get tight.
He has been wearing 12 month clothes since around 9 months old, he is still wearing them now. But I am going to get out his 18 month clothes in the next couple of weeks...right around his 1 year birthday I guess.