NCC Certified Electronic Fetal Monitoring (C-EFM) Practice Exam

Fetus can survive in an environment with a PO2 equal to adult venous blood due to?

1. Low Metabolic Rate

2. Increased O2 Carrying Capacity

3. Polycythemia

4. High Hemoglobin Levels

The correct answer is: Increased O2 Carrying Capacity

The correct answer centers around the increased oxygen-carrying capacity of the fetal hemoglobin compared to adult hemoglobin. Fetal hemoglobin (HbF) has a higher affinity for oxygen than adult hemoglobin (HbA), which allows it to effectively extract oxygen from the maternal blood across the placenta, even when the partial pressure of oxygen (PO2) is relatively low, similar to that found in adult venous blood. This higher affinity means that at lower oxygen tensions, fetal hemoglobin can still pick up and carry sufficient oxygen to meet the metabolic demands of the developing fetus. This adaptation is crucial for survival in the lower oxygen environment that is characteristic of the intrauterine condition. The other options, while related to oxygen transport and delivery, do not directly address the mechanism that allows the fetus to thrive in an oxygen-deprived environment. For example, a low metabolic rate could help reduce oxygen consumption, but it doesn't change the ability to transport oxygen effectively. Similarly, polycythemia (an increased number of red blood cells) and high hemoglobin levels can enhance oxygen transport to a degree, but the primary factor that allows the fetus to survive at low PO2 is the unique properties of fetal hemoglobin itself. Therefore, focusing on this