What is the primary cause of late decelerations in fetal heart tracing?

Late decelerations in fetal heart tracing are primarily associated with uteroplacental insufficiency. This condition occurs when there is inadequate blood flow to the placenta, which can lead to decreased oxygen delivery to the fetus. When the fetus experiences a drop in oxygen due to the impaired function of the placenta, it results in a consistent pattern of late decelerations. These decelerations typically occur after a contraction begins and recover after the contraction ends, reflecting the relationship between uterine contractions and fetal heart rate response to compromised oxygenation.

Late decelerations may signal a potential threat to the fetus, necessitating careful monitoring and intervention. Recognizing this pattern as a sign of uteroplacental insufficiency is crucial for managing labor and delivery effectively.

In contrast, head compression can cause variable decelerations, and cord compression may lead to both variable and early decelerations. Maternal anxiety, while it can affect maternal heart rate and overall well-being, does not directly cause the characteristic late decelerations seen on a fetal heart tracing.