AWHONN Foetal Monitoring Exam with Questions and Answers

AWHONN Foetal Monitoring Exam with Questions and Answers Which maternal physiologic process is the primary driving force that enables oxygen to move from the maternal circulation into the fetal circulation across the placenta? a. Active transport of oxygen through placental cells b. Diffusion down a partial pressure gradient c. Endocytosis of oxygen by trophoblasts d. Fetal hemoglobin actively extracting oxygen from maternal blood Correct Answer: b. Diffusion down a partial pressure gradient Rationale: Oxygen transfer across the placenta occurs primarily by simple diffusion. Maternal blood has a higher oxygen partial pressure than fetal blood, creating a gradient that drives oxygen movement across the placental membrane. This physiologic principle is fundamental to maternal-fetal oxygen exchange. A laboring patient develops prolonged maternal hypotension after epidural placement. Which component of the maternal-fetal oxygenation pathway is most directly compromised initially? a. Uterine blood flow to the intervillous space b. Fetal hemoglobin concentration c. Umbilical vein oxygen content d. Fetal pulmonary gas exchange Correct Answer: a. Uterine blood flow to the intervillous space Rationale: Maternal hypotension can significantly reduce uteroplacental perfusion because uterine blood flow lacks strong autoregulation. Reduced maternal blood delivery to the placenta decreases oxygen availability for fetal transfer.