North American Registry of Midwives (NARM) Practice Exam

What is the defining characteristic of late decelerations?

1. Onset occurs predictably with each contraction

2. Onset occurs late in the contraction and extends beyond it

3. It is immediately followed by an acceleration

4. They are always associated with maternal hypertension

The correct answer is: Onset occurs late in the contraction and extends beyond it

Late decelerations are characterized by their timing in relation to uterine contractions. The defining aspect is that the onset of these decelerations occurs after the peak of the contraction and typically extends beyond the end of the contraction. This pattern indicates that the fetal heart rate drops in response to uterine pressure or decreased oxygenation, which can be associated with placental insufficiency or fetal distress. Understanding this timing is crucial for midwives and healthcare providers, as it suggests a potential compromise in fetal well-being, necessitating further assessment or intervention. The fact that they occur after the contraction begins is what sets them apart from other types of decelerations, which may happen at the start or simultaneously with a contraction. The emphasis on this characteristic highlights the importance of continuous fetal monitoring during labor in order to identify and respond appropriately to signs of distress.