Transient Familial Neonatal Hyperbilirubinemia*

Abstract

Eight unrelated mothers were observed giving birth to 24 infants each of whom had severe neonatal unconjugated hyperbilirubinemia of unknown etiology. Four infants developed kernicterus. Beginning in the second trimester of pregnancy, sera from the 8 mothers and their newborn infants inhibited direct-reacting bilirubin and o-aminophenol glucuronide formation by rat liver slices and homogenates, respectively, 4 to 10 times more than was observed with sera from a control group of pregnant women and their infants. The serum inhibitory factor in these women is unidentified. Available data suggest that it is a progestational steroid that inhibits glucuronyl transferase activity in the liver of neonates.