The Etiology of Neonatal Hyperbilirubinemia

Etiology of Physiologic Neonatal Hyperbili­rubinemia. Every newborn infant develop·s hyperbilirubinemia during the first week of life which is called "physiologic". There are several factors responsible for the development of physiologic hyperbilirubinemia, as follows:  1. Increased bilirubin production, due to a - Increased blood volume. b - Decreased R.B.C. survival time.  c - Increased ineffect_ive hematopoiesis.  d. Increased bilirubin production from non-hemoglobin sources.·  2 . Hepatic insufficiency in bilirubin uptake  a - Decreased Y protein in liver cells, or binding of Y protein by other anions.  3. Hepatic insufficiency in bilirubin conjuga­ gation due to  a - Decreased UDP glucuronyl trans­ ferase and UDPG dehydrogenase.  b - Inhibitory effect of maternal steroids  on the activity of glucuronyl trans­ferase.  4. Bilirubin reabsorption from intestine (en­tero-hepatic circulation), due to a - Absence of physiologic bacterial flora  of the intestine.  b - Presence of beta glucuronidase in  the intestine.  c - Decreased motility of the bowls.  5. Hepatic circulation a - Sudden decrease of oxygen supply to  the liver after birth.  b - Portal blood flow bypassing liver through partiaily patent ductus venosus.