Neurological control of fetal heart rate in 20 cases of anencephalic fetuses.

Fetal heart rate (FHR) is influenced by the central nervous system, cardiac automatism, biochemical factors, etc. Changes in FHR were correlated with the anatomic defect in autopsy material from 20 anencephalic infants, and, on this basis, the following hypotheses were formed, subject to later experimental proof. (1) The FHR baseline level is controlled by the medulla oblongata and vagus nerve. (2) The biphasic sleep-awake pattern is controlled by the cerebral cortex. (3) The midbrain is involved in the occurrence of acceleration. (4) A relative high level of short-term variability is shown when small lesions of the lesser central nervous system are present, but we cannot conclude that the cortex is critical for short-term variability. On the other hand, long-term variability seems to be correlated to the presence of the medulla oblongata and midbrain, and might be amplified by the cerebral cortex. (5) U-shaped decelerations are connected with the medulla oblongata, but V-shaped decelerations depend on intracardiac reflexes and myocardial stretch.