What is the definition of polycythemia in newborns?

Polycythemia in newborns is defined as a condition characterized by an elevated hematocrit level. Specifically, a peripheral venous hematocrit greater than 65% is used as the threshold for diagnosing polycythemia in neonates. This elevated level indicates that there are more red blood cells than normal, which can have implications for the newborn's health, such as increased blood viscosity and associated risks, including poor oxygen delivery to tissues.

The choice of a hematocrit level above 65% reflects clinical consensus that identifies polycythemia based on its potential effects and complications in newborns. High hematocrit may necessitate further evaluation and management to address any associated risks, such as jaundice or respiratory issues.

In contrast, while a hematocrit greater than 60% is also high, it does not meet the specific definition utilized to classify polycythemia. The other provided options do not accurately reflect the definition of polycythemia; autoimmune hemolytic anemia is a distinct condition characterized by the destruction of red blood cells, and low hemoglobin levels in the first week of life is not associated with polycythemia but rather indicates anemia. Therefore, focusing on the specific level of hematocrit is crucial