What percentage of fetal hemoglobin is typically present in a neonate born at 28 weeks gestational age?

• A. 30%
• B. 70%
• C. 100%
• D. 50%

Answer: (C)

Fetal hemoglobin is the dominant form of hemoglobin during fetal life, and in very preterm neonates the switch to adult hemoglobin has not yet progressed. At 28 weeks of gestation, almost all circulating hemoglobin is HbF, so the percentage is effectively near 100%. After birth, HbF gradually declines as HbA production ramps up and becomes the predominant form over the ensuing weeks and months. This high HbF level in preterm infants helps facilitate oxygen transfer in utero, reflecting the ongoing maturation state of hemoglobin synthesis.