Certified Hyperbaric Technologist Practice Test

How does the half-life of fetal carboxyhemoglobin (CBHgb) compare to that of the mother?

1. Shorter than the mother's

2. About the same as the mother's

3. Longer than the mother's

4. Non-comparable

The correct answer is: Longer than the mother's

The half-life of fetal carboxyhemoglobin (CBHgb) is longer than that of the mother due to several physiological differences between the two. In a developing fetus, the presence of fetal hemoglobin (HbF) contributes to altered binding characteristics with carbon monoxide (CO). Fetal hemoglobin has a higher affinity for CO compared to adult hemoglobin, which means that once CO is bound to fetal hemoglobin, it is released much more slowly than it is from the mother’s hemoglobin. Additionally, the fetal metabolic rate and the placental barrier can also influence the accumulation and dissipation of carbon monoxide, leading to prolonged effects in the fetus. As such, if CO exposure occurs, the fetus will retain carboxyhemoglobin for a longer duration than the mother. This difference is critical in clinical settings, particularly in cases of carbon monoxide poisoning in pregnant individuals, as it emphasizes the importance of prompt treatment to mitigate risks to the developing fetus.