Icterus neonatorum; its incidence and cause.

In spite of the frequency of icterus neonatorum and the work done to elucidate the problems connected with it, there still remains much divergence of opinion regarding its incidence and pathogenesis. Estimates of the incidence vary from 40 to 80 per cent. of the nYewborn. Since the detection of jaundice is influenced by many factors, such as the vascularity of the skin and the nature of the light in which the observation is made, and since there are several definitions of jaundice, such varying estimates are not surprising. Icterus neonatorum has been ascribed to excessive haemolysis of the blood, to immaturity of the liver, to increased viscosity of the bile, and to the breakdown of the mother's blood in the placenta. The hypothesis that the jaundice was hepatic in origin has been replaced by one that it is caused by excessive haemolysis. Since bilirubin is a product of the breakdown of haemoglobin, all jaundice may be said to be the result of haemolysis, but the evidence of excessive haemolysis as a cause of icterus neonatorum is inconclusive. During the past year, in the course of biochemical and haematological investigations of haemolysis, there occurred an opportunity to study newborn babies, and an investigation of icterus neonatorum was undertaken, (1) to determine the incidence, (2) to try to detect any difference in the rate of haemolysis in jaundiced and non-jaundiced infants, and (3) to seek evidence of impairment or immaturity of liver function.