The Influence of Birth Weight and Gestational Age on Kidney Function in Premature Infants

Introduction. The impact of prematurity on the functional state of the kidneys in infants has not yet been sufficiently studied. Aim. To determine the influence of birth weight and gestational age on the creatinine level in the blood and glomerular filtration rate (GFR) in early childhood. Materials and methods. A retrospective analysis was conducted on medical records of 316 children aged from 1 month to 1.5 years, hospitalized at the Department of Early Childhood Pathology (National Medical Research Center for Children’s Health, Moscow) from 2012 to 2020 due to consequences of perinatal CNS damage. Children without congenital kidney diseases, with normal urine values in medical history, without structural abnormalities on ultrasound were included in this study. Serum creatinine was determined by the enzymatic method, GFR - by the Schwartz’s formula using a coefficient of 0.413, as well as, previously proposed coefficients of 0.33 for premature and 0.44 for full-term infants. Results. In premature infants, notably born with extremely low birth weight and very low birth weight, at the age of 1 year, serum creatinine is reduced compared to full-term infants, GFR in deep-premature infants exceeds the level of GFR in full-term infants by the year. The results allow concluding the method of calculating GFR by formulas based on serum creatinine to be invalid. Due to possible hyperfiltration in preterm infants, they need regular monitoring urine tests, blood pressure, due to the risk of developing chronic kidney disease. Conclusions. It is necessary to search for other methods for determining GFR in extremely premature infants. The established indices of the blood creatinine content can be used as reference values for different periods of gestation and body weight at birth in institutions using the enzymatic method for determining blood creatinine. The obtained GFR indices as a reference can be recommended for full-term and premature babies born after 32 weeks of gestation and with a birth weight of more than 1500 g.