My oldest son only weighed 3 lbs 7 1/2 ozs when he was born in 1976 but was not a premature baby. He was born with kidney disease and two birth defects that required surgery to correct. One was corrected when he was 3 so that his lungs could expand more and give him more oxygen. His chest looked like a deep V instead of a flat chest wall. He stayed smaller than his brother and sister. When he was 16 months old his sister was born and by the time she was 6 months old, she was as big as he was. He is 34 will turn 35 in May and weighs 93 lbs. He has never weighed more than 100 lbs in his life. When he was 24 he had to have a kidney transplant on Sept 2, 2000.