Chapter 190 Fetal Heart Rate Testing: Periodic Changes
INTRODUCTION
Description: Periodic changes in the fetal heart rate in conjunction with uterine contractions may occur. These may indicate fetal stress when they are persistent, are progressively deeper, or become longer lasting. Recurrent decelerations are defined as occurring with ≥50% of contractions during a 20-minute period. In the United States, decelerations in the fetal heart rate are classified by their relationship to uterine activity: early, late, and variable. The shape of the deceleration is also significant in the classification. Accelerations higher than the baseline often accompany fetal movement and are reassuring.
Prevalence: Mild and transient periodic decelerations are not uncommon during the course of normal labor. Accelerations are documented in virtually all normal labors.
