Late Decelerations

Excerpt

Late decelerations are among the most concerning of the 3 types of fetal heart rate decelerations during labor. They are caused by decreased blood flow to the placenta and can signify an impending fetal acidemia.

Definition

Late deceleration is defined as a visually apparent, gradual decrease in the fetal heart rate that typically follows a uterine contraction. The gradual decline is defined as a period from onset to nadir that takes 30 seconds or more. A late deceleration typically follows a uterine contraction, meaning the onset, nadir, and return of the deceleration follow the onset, peak, and return of a uterine contraction. Typically, late decelerations are shallow, with a slow onset and a gradual return to the normal baseline. The usual cause of the late deceleration is uteroplacental insufficiency.