What happens to normal embryonic hemoglobin before birth?

Normal embryonic hemoglobin, primarily consisting of hemoglobin E and F, plays a crucial role in early development. Before birth, as the fetus grows and matures, embryonic hemoglobin is gradually replaced by fetal hemoglobin. Fetal hemoglobin (HbF) has a higher affinity for oxygen compared to embryonic hemoglobin, which is essential for effective oxygen transport from the mother to the developing fetus. This transition is critical for ensuring that the fetus receives adequate oxygen during gestation.

The production of fetal hemoglobin begins around six weeks of gestation and continues to replace embryonic hemoglobin as the pregnancy progresses. By the time of birth, most of the hemoglobin present in the newborn is fetal hemoglobin, which eventually transitions to adult hemoglobin after birth.

This process underscores the developmental adaptations in the hemoglobin types that are necessary for optimal oxygen delivery in varying stages of life, with embryonic hemoglobin being phased out in favor of fetal hemoglobin before birth.