A single-center prospective cohort study was designed to identify alterations of renal function during childhood in children born prematurely. A cohort of 143 such babies born over a 4-year period (birth weight less than 1000 g and/or less than 30 weeks of gestation) was prospectively included at birth. A mailing was sent to all parents to propose renal evaluation. Among the 50 included children, 23 had intrauterine and 16 had extrauterine growth retardation. When comparing both of these groups to 11 children with appropriate pre- and postnatal growth at a mean follow-up of 7.6 years, both groups of growth-restricted children had slightly but significantly lower glomerular filtration rates, measured by inulin clearance, although both groups were still within the normal range for their ages. There were no differences for other renal parameters, neonatal therapies or complications, except for postnatal corticosteroid exposure. Children with extrauterine growth restriction were found to have significantly lower protein-energy intake during their first week of life than the intrauterine growth-restricted or the normotrophic children. Our study found that children with either intra- or extrauterine growth retardation are at risk of decreased glomerular filtration rates during childhood. Extrauterine growth restriction represents a new risk factor for long-term renal impairment in premature children.