ABSTRACT
Fetal development occurs in a relatively hypoxemic environment, and many contributing factors enable adequate oxygen delivery to essential organs and tissues to ensure optimal growth. The high oxygen affinity of fetal hemoglobin facilitates oxygen uptake in the placenta, and the characteristic oxyhemoglobin dissociation curve optimizes oxygen unloading at the tissue level. An intricate system of circulatory shunts and streaming of relative oxygen-rich blood toward the left heart maintain cerebral oxygen delivery. In the presence of congenital heart defects, disruption of streaming could lead to hypoxic brain injury and stunted brain growth, raising the possibility of maternal hyperoxygenation therapy as a means to improve fetal cerebral oxygen delivery. The fetus has evolved to thrive in a hypoxemic environment and attempts to raise the fetal blood oxygen tension to supraphysiological concentrations may have untoward effects.
