Postnatal Kidney Function in Children Born Very Low Birth Weight

Introduction. There are scarce data on estimating the time of completing kidney maturation in very-low-birth-weight (VLBW) infants. The aim of this study was to determine whether different aspects of kidney function differ between VLBW infants and normal babies at 18 to 30 months postconceptional age.Materials and Methods. This study was carried on 23 VLBW infants and 21 normal-birth-weight infants at 18 to 30 months corrected postconceptional age, who were born between June 2007 and June 2008 at Alzahra Hospital and Shahid Beheshti Hospital, in Isfahan, Iran. Very low birth weight was defined as a birth weight between 1000 g and 1500 g, while gestational age is less than 32 weeks. In both groups, children with a history of sepsis, asphyxia, intubation, hypoxic ischemic encephalopathy, and pyelonephritis were excluded.Results. The mean of systolic, diastolic, and mean arterial blood pressure were not significantly different between the two groups. Urine calcium-creatinine ratio, fraction excretion of magnesium, and renal threshold for phosphate were significantly higher in the VLBW children compared with the control group. Glomerular filtration rate was higher in the control group than in the VLBW group.Conclusions. Our results demonstrated that in VLBW children at the corrected age of 24 ± 6 months, some aspects of tubular and glomerular functions are still impaired. Longer longitudinal cohort studies on VLBW are required to determine the time of completing kidney function maturation in these children.