Prolonged Neonatal Unconjugated Hyperbilirubinemia Associated with Breast Feeding and a Steroid, Pregnane-3 (Alpha), 20 (Beta)-Diol, in Maternal Milk That Inhibits Glucuronide Formation In Vitro*

Abstract

A syndrome of severe and prolonged unconjugated hyperbilirubinemia has been described in association with breast feeding in 7 unrelated newborn infants. Milk obtained from the mothers of the 7 infants consistently inhibited glu-curonyl transferase activity in vitro when compared with 99 specimens of milk obtained from 71 women whose infants did not demonstrate this syndrome. A steroid that competitively inhibits glucuronyl transferase activity in vitro has been isolated from inhibitory but not from nonin-hibitory human milk. The steroid has been identified as pregnane-3(alpha), 20(beta)-diol.