Free
estradiol and
estriol was determined radioimmunologically in cord blood and in peripheral venous blood during the third, fifth and seventh day of life. The
steroid level of a group of children with
icterus neonatorum simplex were compared with an anicteric control group. In spite of the higher level of
estriol in cord blood during the first week of life,
estriol was eliminated much more rapidly than
estradiol and independent of the
bilirubin level. Given the same initial values for
estradiol in cord blood of both control groups, the
estradiol elimination rate was significantly slower in icteric newborns. The level of
estradiol in cord blood was significantly higher in newborn males than in newborn females. A higher level in cord blood, however, does not increase the risk of a later newborn
hyperbilirubinemia. Our findings tend to indicate that no etiologic importance should be attached to the amount of
estradiol and
estradiol to be eliminated, for the development of
icterus neonatorum simplex. At the same time, icteric newborns have a relative insufficiency in
estradiol elimination but not, however, in
estriol elimination.