Postnatal renal function in preterm newborns: a role of diseases, drugs and therapeutic interventions

Since few data are available about factors affecting renal maturation especially in the lower gestational ages (G.A.), the aim of this work was to study postnatal renal function in a representative population sample of preterm newborns (G.A. <= 36 weeks), admitted to the neonatal intensive care units of seven Italian hospitals, in order to investigate a possible role of drugs, therapeutic interventions and diseases. Data were collected through detailed questionnaires including maternal and neonatal information. To test renal function, serum creatinine and urine output were regularly recorded every 3 days throughout the 1st month of life. A total of 246 subjects were enrolled in the study and divided into four groups according to G.A.: group A, 22-25 weeks; group B, 26-28 weeks; group C, 29-32 weeks; group D, 33-36 weeks. Serum creatinine concentrations at birth were similar in all four groups, while significant differences were evident from the 3rd to the 21st day of life. Within each group, two subpopulations were identified taking into account creatinine values. In subjects with serum creatinine concentrations within the normal range, a physiological decline in creatinine values was observed with increasing postnatal age, and an inverse correlation between creatinine and G.A. was evident from the 3rd day of life to the end of the study period. In neonates with impaired renal function, a marked increase in creatinine values was observed in all neonates from the 3rd day of life, with significant differences among groups on days 7 and 10. Whereas many risk factors were correlated (univariate analysis) with impaired renal function, the multivariate analysis identified only five factors as independent: maternal consumption of nonsteroidal anti-inflammatory drugs (NSAIDs) during pregnancy [odds ratio (OR): 7.38, 95% confidence interval (CI) 3.26-16.7] and intubation at birth (OR: 4.39, 95% CI: 1.2-16.3) were the main risk factors. Respiratory distress syndrome, a low Apgar score and ibuprofen treatment of the neonate were identified as additional risk factors. Our data confirm a multifactorial origin of acute renal impairment in newborns. It is of note that pharmacological treatment with NSAIDs during pregnancy may negatively influence neonatal renal function.