What is indicated if fetal heart tones are normal at the start but dip at the peak of contractions?

When fetal heart tones are observed to be normal at the start but dip at the peak of contractions, this pattern indicates late decelerations. Late decelerations are characterized by a gradual decrease in the fetal heart rate that occurs after the peak of a contraction, returning to baseline only after the contraction has ended. This pattern suggests that there may be placental insufficiency or fetal distress, as the drop in heart rate indicates that the fetus is not receiving adequate oxygen during the contractions.

In contrast, early decelerations typically coincide with the beginning of a contraction and are often a result of head compression during labor, reflecting a normal physiological response rather than an indication of distress. Variable decelerations are abrupt decreases in heart rate that can occur at any point during the contraction cycle, often associated with cord compression. Identifying these differences is crucial for monitoring fetal well-being during labor and deciding on potential interventions. A normal fetal heart rhythm would not present with such dips during contractions, hence it does not apply in this scenario.