My GF got referred to her paed for the same thing, for both of her kids, and in her case all they paed didi was look at the child, ask what the mum was doing there, and tell her her kids were perfectly fine, just small and petite.

I think they just have to be overly cautious, JIC. I do know of a girl who stopped growing at a certain age (very young) and needed medical intervention etc for her condition (not sure what It was but she's tall now and just went to ehe US on a scholarship to play college basketball)