Postnatal development of renal function in preterm and term neonates

The study was done to determine the renal function in preterm and term newborn infants in the neonatology unit of the Department of Paediatrics and Labour Ward of the Department of Obstetrics and Gynaecology, Bangabandhu Sheikh Mujib Medical University (BSMMU) during the period of February 2002 to February 2003. Sixty physiologically stable newborn infants were enrolled in this study, 40 of those were preterm and 20 were term. The gestational ages of preterm and term babies were 35.6±4.7 and 39.10±1.41 weeks respectively. Mean weight of preterm babies was 1840±410 gm and term babies was 3150±340 gm respectively. Male to female ratio was1.6:1. The concentration of serum creatinine was high during the first week of life in both the term and preterm babies. The concentration decreased in both the groups during the subsequent 3 weeks. Although creatinine values were significantly high in preterm babies than the term babies at first week (p<0.001), the values reach to almost similar at 3rd week of life. A negative correlation was found between serum creatinine and gestational age (r=0.86, p<0.001). Creatinine clearance was found low at birth, the lowest values being observed in the most premature infants (p<0.0001) and was increased in the subsequent 3 weeks of the study period. Creatinine clearance showed a positive correlation to gestational age from the first week onwards (r=0.87, p<0.001). Fifteen percent preterm babies were hyponatraemic and in all term babies serum level of sodium was within normal limit. Fractional excretion of sodium was high in preterm neonate than the term neonate especially in early weeks of life (p<0.001). The value correlated negatively to gestational age (r=0.67, p<0.001). It was evident from the present study that the renal function is significantly lower in preterm neonates than term neonates. The study also indicates that the maturation of renal function occurs earlier in the term babies than the preterm babies.