my 4 month old baby girl's weight is 4800g. she is preterm baby and her birth weight was1700g. is she underweight?

A. Your child is having a very good weight gain just to get the birth weight being a mature child and the weight gain now it should be 500 g minimum for a normal child’s full term child and you are a premature child is gaining so good which is excellent so please don’t worry about it