Heart rate patterns of normal fetuses reflect physiological responses to various endogenous and exogenous stimuli.5 The normal baseline record of FHR provides evidence that intrinsic control mechanisms responsible for cardiovascular autoregulation are intact. Control of FHR requires electrical conduction pathways, cellular receptors to circulating neurohormones, reflex arcs, and inherent myocardial contractility.5 The use of specific FHR patterns to evaluate fetoplacental status is based on the association of their components with particular intrauterine events or conditions. These components include baseline rate, rate variation, and episodic rate responses to fetal movements (accelerations) or uterine contractions (decelerations). The characteristics of these FHR components are determined by both cellular and systemic mechanisms.