Final answer:
Fetal hemoglobin is found to the left of maternal hemoglobin on an oxygen-hemoglobin dissociation curve, signifying its higher affinity for oxygen.
Step-by-step explanation:
On an oxygen-hemoglobin dissociation curve, fetal hemoglobin (Hb) is positioned to the left of maternal hemoglobin (Hb). This leftward shift indicates that fetal hemoglobin has a greater affinity for oxygen compared to maternal hemoglobin. Due to its different structure, fetal hemoglobin binds oxygen more readily, ensuring efficient transfer of oxygen from the mother to the fetus.
The maternal blood in the placenta has a lower partial pressure of oxygen (about 35 to 50 mm Hg) compared to the maternal arterial blood. Despite that, the fetus can effectively extract oxygen since its hemoglobin's higher affinity allows it to saturate at these lower partial pressures (about 20 mm Hg for fetal blood at the placenta). The oxygen-hemoglobin dissociation curve graph is sigmoidal in shape, showing a rapid increase in the percentage of oxygen-saturated hemoglobin with increasing oxygen partial pressures.