What is the lifespan of RBC in newborn?

In newborns, the lifespan of red blood cells (RBCs) is relatively shorter compared to adults. The average lifespan of RBCs in newborns is approximately 80-90 days, while in adults, it is around 120 days.

This difference in lifespan is primarily attributed to the presence of fetal hemoglobin (HbF) in newborn RBCs. HbF is the predominant hemoglobin type during fetal development and in the early postnatal period. It has a higher affinity for oxygen than adult hemoglobin (HbA), which allows the fetus to extract oxygen from the maternal circulation. However, HbF is less stable and has a shorter lifespan than HbA.

As the newborn transitions to breathing air after birth, the production of HbF decreases, and the production of HbA increases. This gradual switch from HbF to HbA is known as hemoglobin switching or the "HbF-to-HbA switch." As more RBCs containing HbA are produced, the older RBCs containing HbF are gradually removed from circulation. This process contributes to the shorter lifespan of RBCs in newborns.

By 2-3 months of age, the majority of RBCs in the newborn's circulation contain HbA, and the lifespan of RBCs becomes comparable to that of adults. However, some residual HbF may still be present in the circulation for several months after birth.