My daughter is 2, since potty-training, now all she can really wear are dresses and leggings. She's a skinny mini. She's in size 3T for length, and I'm buying 4T shirts for summer to make sure they last the whole season. Her summer bottoms from last year, size 18m & 2T, I think will all fit her again this year!  I bought another couple 2T skirts over the weekend, they barely stay up without the diaper bulk!  Same with swimsuit, got a 2T 2-peice and it's still a little baggy.  She's perfectly healthy, eats well, just tall and thin. She's been the same ratios since she was a baby.