NATURAL CAUSE OF NEONATAL POLYCYTHEMIA

Background: A capillary hematocrit (cap HCT) > 65 % may be associated with potentially life-threatening hyperviscosity. What is the frequenc y and relevance of a cap HCT > 65 % in healthy newborn infants? What i s the natural course of the HCT within the first days of life? Methods : In a prospective study, cap HCT was determined in 207 healthy newbor n infants on day 1 and 5. The data were correlated to minor symptoms o bserved on day 1, to weight loss from birth to day 5 and fluid intake during the first 96 hours. A venous blood sample was taken to confirm polycythemia, if cap HCT was > 65 %. Results: 19/207babies had a cap H CT > 65 %. In 7 of these 19 babies venous HCT was also greater than or equal to 65 %. All of these 7 babies had a cap HCT greater than or eq ual to 70 %. There was no association between polycythemia and clinica l minor symptoms. A significant decrease of HCT from day 1 to day 5 wa s observed, which was not related to weight loss and fluid intake, but was positively correlated to HCT on day 1. Conclusions: A cap HCT > 6 5 % is a frequent finding in healthy newborn infants, A true polycythe mia, however, was only observed, if cap HCT was greater than or equal to 70 %. HCT values decreased significantly during the first days of l ife, particulary, if the values were high on day 1. In borderline-case s (venous HCT > 65 % and < 70 %) it may be justified to wait and see.