Neonatal red cell transfusion
Neonates are defined as babies up to 28 days after birth. Most extremely preterm babies (less than 28 weeks) require at least one red cell transfusion; this is partly due to the amount of blood removed with blood samples compared to the baby's total blood volume (iatrogenic anemia) and partly due to anemia of prematurity.
Source: Wikipedia — Neonatal red cell transfusion (CC BY-SA 4.0)