Which type of deceleration begins and ends with the contraction?

Early deceleration is characterized by a gradual decrease in fetal heart rate that begins and ends with uterine contractions. This type of deceleration is typically associated with fetal head compression. The mechanism behind early decelerations involves increased intracranial pressure as the fetal head descends during contractions, which triggers a reflex mediated by the vagus nerve, leading to a temporary decrease in heart rate.

In contrast, late decelerations occur after a contraction has begun and do not return to baseline until after the contraction has ended, suggesting potential placental insufficiency or fetal distress. Variable decelerations are abrupt drops in heart rate that can occur regardless of contractions and are typically caused by umbilical cord compression. Prolonged decelerations are defined as a decrease in heart rate lasting longer than 2 minutes but less than 10 minutes and are not directly related to contractions. Thus, early deceleration is uniquely identified by its synchronous relationship with uterine contractions, making it the correct choice.