Intrauterine growth restriction: Adverse effects on renal growth and function in preterm infants.

Abstract

Aim: The aims of this study were to 1) characterise the effects of intrauterine growth restriction (IUGR; birth weight below the 10th percentile for gestational age) on nephron formation (nephrogenesis) in the developing human kidney, and 2) assess the impact of IUGR on kidney growth and function in preterm neonates during the first month of life. Background(s): IUGR is a common co-morbidity of preterm birth (delivery prior to 37 completed weeks of gestation). To date, very few studies have examined the specific impact of IUGR on the development of the human kidney. Furthermore, the combined impact of IUGR and preterm birth on postnatal kidney growth and function is largely unknown. Method(s): Kidney tissue collected at autopsy from non-IUGR (n=51) and IUGR (n=39) infants at 20-41 weeks gestation was histologically examined to assess nephrogenesis. Additionally, kidney size (ultrasonography) and function (urinary protein excretion) were assessed in non-IUGR (n=21) and IUGR (n=16) neonates born preterm, on days 8 to 29 of life. Result(s): IUGR infants exhibited significant reductions in kidney weight and glomerular generation number during gestation, indicative of reduced nephron formation. IUGR neonates born preterm had significantly elevated low molecular weight protein (beta-2 microglobulin) excretion compared to non-IUGR preterm neonates on days 8, 15 and 22 of life, suggestive of tubular dysfunction. Kidney size was not different between groups at postnatal day 8; however, the width and volume of the right kidney was significantly reduced in IUGR preterm neonates on postnatal day 29. Conclusion(s): These findings highlight the importance of maintaining optimal body growth during late gestation, for adequate in utero renal development as well as postnatal kidney growth and function following preterm birth.