Features of Bilirubin Metabolism in Newborns with Intrauterine Growth Restriction

Abstract

Intrauterine growth restriction is also an important neonatal condition that relates to impaired metabolic adaptation after birth. Among the early problems encountered by the growth-restricted infants, there are disturbances in the metabolism of bilirubin that are quite relevant because of the risk of exaggerated neonatal jaundice. This study was conducted to assess the characteristics of total bilirubin and its components in newborns with intrauterine growth restriction and compare the results with those of the infants appropriate for gestational age. A prospective comparative study was performed from January 2024 to November 2025, including 90 term newborns. The key group was the 45 babies who were diagnosed to have intrauterine growth restriction, whereas the 45 newborns that were appropriate for gestational age were the control group. Serum total bilirubin, direct bilirubin and indirect bilirubin levels were measured between the third and fifth days of life by using standardised laboratory methods. Newborns with intrauterine growth restriction showed significantly more total and indirect bilirubin levels than did controls. The predominance of unconjugated hyperbilirubinemia is suggestive of delayed hepatic conjugation activity in growth-restricted infants. A higher percentage of IUGR newborn babies developed moderate to severe hyperbilirubinemia and required phototherapy. In addition, there was a negative correlation between levels of bilirubin and birth weight percentile among the IUGR group. The results show that bilirubin metabolism in growth-restricted newborns differs from that of infants with normal intrauterine growth. Careful biochemical monitoring during the early neonatal adaptation process may help in the timely intervention and limit the risk of developing complications related to bilirubin in this delicate population.