Early decelerations are most commonly caused by which mechanism?

Early decelerations are most commonly caused by which mechanism?

• A. Cord compression
• B. Placental abruption
• C. Head compression during contractions
• D. Uterine rupture

Answer: (C)

Head compression during contractions. When the fetal head is squeezed as a contraction builds, intracranial pressure rises and stimulates the fetal vagus nerve, causing a brief slowing of the heart rate. This deceleration starts with the onset of the contraction and recovers as the contraction ends, so it mirrors the contraction pattern. This pattern is usually benign and common in labor. Cord compression typically causes abrupt, variable decelerations that are not consistently tied to contraction timing. Placental problems produce late decelerations that begin after the peak of a contraction and do not recover until after the contraction ends, signaling uteroplacental insufficiency. Uterine rupture presents with sudden, severe fetal distress and maternal instability, not the predictable mirror image seen with head compression.

Head compression during contractions. When the fetal head is squeezed as a contraction builds, intracranial pressure rises and stimulates the fetal vagus nerve, causing a brief slowing of the heart rate. This deceleration starts with the onset of the contraction and recovers as the contraction ends, so it mirrors the contraction pattern. This pattern is usually benign and common in labor.

Cord compression typically causes abrupt, variable decelerations that are not consistently tied to contraction timing. Placental problems produce late decelerations that begin after the peak of a contraction and do not recover until after the contraction ends, signaling uteroplacental insufficiency. Uterine rupture presents with sudden, severe fetal distress and maternal instability, not the predictable mirror image seen with head compression.