My son is two months old hes super skinny but is the length of a nine month. why isnt he gaining fat?

Longer than heavier: Your son may be gaining height faster than weight which makes him look skinny. The best way to determine proper weight and height gain is to look at their growth curve. Your next doctor's appointment have your health care provider review his growth curves.

Length of 9 mo??: Babies squirm quite a bit. Unless an infantometer is used to measure the baby's length, there's a high rate of wrong measures. This is particularly true when the "pencil and paper" method is used - someone will pencil a line on the paper where the head is and where the feet are then measure the distance between the marks. Often growth curves look more like ekg's then growth charts like this.