Q: When my 9-year-old son was born, he weighed in at 2.8 pounds and has always been underweight.  Over the last 6 months or so he seems to have gained quite a bit of weight and now has a prominent belly. Is this sudden change okay considering his small size at birth?

A: Birth weight only has an impact on survival early on at birth. Afterwards, unless there is any congenital problem that can affect the growth and development, the child should develop and weigh according to the environmental factors of eating habits and activity.