Define polycythemia in neonates, possible causes, and a common clinical consequence.

• A. Polycythemia is decreased hematocrit; cause dehydration; consequence hypotension.
• B. Polycythemia is elevated hematocrit (>65% term or >70% preterm); causes placental insufficiency, maternal diabetes, delayed cord clamping; consequence hyperviscosity leading to poor perfusion and organ dysfunction.
• C. Polycythemia is elevated white blood cell count; cause infection; consequence sepsis.
• D. Polycythemia is normal hematocrit; cause prematurity; consequence sedation.

Answer: (B)

Polycythemia in neonates means an excess of red blood cells, resulting in a high hematocrit. In term babies, this is typically defined as a hematocrit greater than 65%, and greater than 70% in preterm infants. The thicker blood from more red cells increases viscosity, which slows flow through small vessels and reduces tissue perfusion. The most common clinical consequence of this hyperviscous state is impaired perfusion that can lead to organ dysfunction.

Classic causes include placental insufficiency, which creates chronic fetal hypoxia and stimulates the production of more red cells; maternal diabetes, which is associated with fetal hypoxia and increased red cell mass; and delayed cord clamping, which increases the newborn’s blood volume and red cell count. These scenarios align with how polycythemia develops and why it can lead to hyperviscosity and perfusion-related problems.

Other options misstate the condition or its effects—for example, defining polycythemia by a low hematocrit, or by white blood cell count, or implying normal hematocrit with a different cause—so they don’t fit the defining features and consequences as described here.