Which type of fetal heart rate deceleration is considered nonreassuring during a contraction stress test?

Late fetal heart rate decelerations are considered nonreassuring during a contraction stress test because they indicate a potential compromise in the fetal oxygen supply, usually associated with uteroplacental insufficiency. In this context, a late deceleration is defined as a decrease in fetal heart rate that begins after the onset of a contraction and returns to baseline after the contraction has ended. This pattern suggests that the fetus may not be tolerating the stress of contractions well, raising concerns about its well-being.

In contrast, early decelerations are typically considered benign and are often associated with fetal head compression during contractions, which does not suggest any distress. Baseline heart rate refers to the overall average fetal heart rate between decelerations and accelerations, and variable decelerations, while they can indicate umbilical cord compression, are not universally classified as nonreassuring in the same way that late decelerations are. Therefore, late decelerations distinctly highlight potential fetal distress, making them an important focus during evaluation in a contraction stress test.