The purpose of this study is to determine if sequence variations in genes involved in the development and function of vulnerable organs increases susceptibility to chronic lung disease (CLD) and other diseases affecting premature infants, such as necrotizing enterocolitis (NEC), sepsis, patent ductus arteriosus (PDA) and intraventricular hemorrhage (IVH). The study will also determine whether measurement of certain biomarkers in serum will identify infants who will develop these complications of prematurity. Previous studies from this institution and others have identified genetic variants in some genes, such as toll like receptor genes are associated with higher risk of CLD or NEC. The interaction of these variants with other gene variants that can influence the risk of these diseases remains unclear.