Specific Aims The long-term goal is for early diagnosis of those infants who are at risk for future development of hypertension and kidney disease so that investigators might intervene to potentially avert progression to adult disease. The objective of this clinical trial is to acquire data on the natural history of neonatal kidney function and size in infants born preterm during the first year of life. This will be done through the use of standard serum and urine markers as well as non-invasive ultrasound technology. The central hypothesis of this clinical trial is that a subgroup of patients born preterm will demonstrate early markers of kidney injury including elevated serum cystatin C, proteinuria and hypertension. This hypothesis has been formulated on the basis of preliminary data from the group studying this question retrospectively in older children born prematurely who have developed overt kidney disease. The rationale for the proposed research is to develop early serum and demographic markers of pre-clinical kidney disease so that early intervention may occur.