What type of deceleration is characterized by the nadir corresponding to the peak of a contraction?

Early decelerations are characterized by a clear relationship between the fetal heart rate deceleration and uterine contractions. Specifically, the deceleration begins before the peak of the contraction and returns to baseline by the end of the contraction, with the lowest point or nadir of the deceleration aligning exactly with the peak of the contraction. This type of deceleration is typically seen as a reassuring sign and indicates that the fetus is experiencing head compression during contractions, which is a common and generally benign physiological response during labor.

In contrast, late decelerations are associated with uteroplacental insufficiency and occur after the peak of the contraction, resolving only after the contraction ends. Variable decelerations are characterized by abrupt decreases in fetal heart rate that are not directly related to contractions and can be caused by umbilical cord compression. Prolonged decelerations indicate a drop in heart rate lasting more than 2 minutes but less than 10 minutes and could reflect various complications depending on the clinical context. Understanding these distinctions is crucial for proper fetal monitoring and assessment during labor.