Late Deceleration

Abstract

A late deceleration, also called “type II dip” or “late dip” is a typical slowdown of the FHR tracing coinciding with uterine contractions (Figure 14-1). The relationship between the uterine contraction recording and the beginning of the deceleration is the determinant factor to classify the FHR alteration as a late deceleration. Characteristically, the FHR starts the deceleration after the intrauterine pressure tracing has passed its maximum value. The FHR slows down smoothly, and reaches its lowest point between 20 and 90 sec after the peak of the uterine contraction tracing. This lag time depends, of course, on the degree of fall in the FHR, which is always slow and regular. The lowest part of the tracing is usually roundish, followed by a slow recovery toward the baseline, which is reached in about 20 to 90 sec, and occasionally longer. The overall aspect of the deceleration (at the standard 1 cm/min paper speed) is that of an open V with a rounded bottom, and a total duration of approximately 1 min.