Early decelerations during fetal monitoring are associated with which mechanism?

• A. Fetal hypoxemia
• B. Increased SVR
• C. Hyperkalemia
• D. Transient increases in fetal intracranial pressure

Answer: (D)

Early decelerations reflect a vagal response to head compression during contractions. As the fetal head is compressed, intracranial pressure rises transiently, stimulating the vagus nerve and causing a brief slowing of the heart rate. The nadir of the deceleration occurs at the peak of the contraction, and this pattern is generally benign. This is in contrast to late decelerations, which are associated with placental insufficiency and fetal hypoxia. The other options don’t fit the mechanism: fetal hypoxemia is linked more with late decelerations; increased SVR and hyperkalemia aren’t the cause of this contraction-synchronous, vagal-mediated slowing.