Abstract Since 1893 when Von Winckel 1 drew attention to the association of fetal bradycardia with poor fetal outcome, slowing of the fetal heart rate to less than 100 beats per minute between contractions has been considered the chief criterion of fetal distress. 2 Application of this dictum to clinical obstetrics has produced a number of seeming inconsistencies, for bradycardia of this magnitude has been frequently noted both in the antepartum period and during labor, yet the infant has been in good condition at birth. In preliminary reports of the electronic evaluation of the fetal heart rate by continuous recording, 3, 4 an attempt was made to differentiate physiologic and pathologic bradycardia by their respective V and U shaped patterns. The pathologic fetal bradycardia which was discussed in detail in these earlier studies was shown to be due to umbilical cord compression. 4 In this report a different type of pathologic fetal bradycardia will be described which is thought to be due primarily to acute fetal hypoxia. A hypothesis will be advanced which may explain the underlying mechanism. However, the need to measure continuously and quantitatively the many factors which may influence the fetal heart rate precludes definite conclusions at this time.
This report describes detailed cardiovascular changes observed in 38 pregnant patients who experienced syncope during postural change from sitting to standing. Sixteen (42%) of the patients had diabetes mellitus. The patients were divided into two groups based on the severity of their symptoms. The 19 who had more severe symptoms had mean arterial pressure (MAP) and MAP-determinant changes that were beyond the 10th and 90th percentile range, while those who had less severe symptoms had lesser cardiovascular changes. Syncope in normal pregnancy is usually short-lived and of little consequence. However, it may provide early warning of a cardiovascular problem. Hence, a simple, convenient cardiovascular test may be a useful adjunct to prenatal care.
In contrast with the fragmentary data obtainable by auscultation, instantaneous, continuous recording of the fetal heart rate through a direct physical connection permits identification both of baseline patterns and deviations—especially certain types of deceleration—associated with fetal distress. The method is now sufficiently reliable to warrant its use at least in all high-risk deliveries.
