To : Ellen Taylor Re : Maternal Bilirubin I would like to add to the discussion of maternal hyperbilirubinemia, bilirubin transfer into milk, and absorption by the infant. First bilirubin will to some degree be secreted into milk, although I have never seen a publication stating the amount. Although it is rather high in molecular weight(584) in the deconjugated form, it is highly lipophilic and I still believe it would be present to some degree. The statement that its molecular weight would preclude its transfer to milk is only partially correct. All kinds of high molecular weight drugs (such as Rocephin = 554) can penetrate quite effectively if they have other physicochemical parameters that aid their transfer through lipid membranes. However, I believe the amount of bilirubin transferred would probably be minimal. But if the infant were hyperbilirubinemic as well, then ... As for the bioavailability of bilirubin, you must remember that bilirubin is easily reabsorbed from the GI tract of an infant during the early neonatal period, it's called enterohepatic reabsorption, but ONLY in its unconjugated form. Breast milk enhances the bioavailability of bilirubin by assisting in its deconjugation, followed by its reabsorption as unconjugated bilirubin. Larry Gartner has published eloquently and extensively on this subject and I urge you all to read his papers. Regards Tom Hale