Early Decelerations

Abstract

The rapid slowdown of the FHR tracing occurring simultaneously with a uterine contraction followed by an equally rapid recovery after an instantaneous low point is called early deceleration of the FHR. It has also been called dip I or cephalic dip. The time relationship between the intrauterine pressure changes and the fall in FHR is crucial to properly classify an alteration manifested as deceleration below the baseline of an otherwise normal looking tracing. The descending arm of the FHR coincides synchronically with the ascending part of the UC tracing, and its lowest point corresponds with the peak of the contraction (Figure 13-1). Following this moment, as the uterus relaxes and the intrauterine pressure falls, there is a rapid recovery of the FHR toward the baseline. The complete cycle of deceleration acquires the shape of a sharp V when the tracing is run at the standard 1 cm/min paper speed (Figures 13-2 and 13-3), and it is slightly U-shaped when the paper runs at 3 cm/min (Figure 13-4).