My first grandchild was born on August 25,2008 weighing 6 lbs., 15 oz. and 20 inches long. He was a full term pregnancy for my daughter-in-law and perfectly healthy. He is now over 4 months old (20 weeks) and my son just brought him home from his check up and told me that the doctor is slightly concerned about the baby's weight. He now weighs 12 lbs. 12 oz. and is 24 and one half inches long. He has never been a breastfed baby but strictly formula which he has always tolerated well. My son and daughter-in-law have only recently (in the past 2 weeks) started adding cereal to his bottles. Should we be overly concerned? Due to the fact that the doctor is "concerned" he requested that my grandson come back for another checkup in one month instead of the normal two months. Just so he can "Keep an eye on his weight". What, if anything, should we do?