The effects of maternal ambulation on the nonstress test.

Using a recently developed noninvasive telemetry device (model 8240A, Hewlett-Packard Co., Palo Alto, California), we studied, under controlled conditions, the effects of maternal ambulation on the nonstress test patterns of 100 near-term high-risk pregnancies, randomly divided into two equal groups who underwent three alternating 30-minute periods of ambulation and bed rest, beginning either with ambulation (group 1) or bed rest (group 2). Fetal heart rate data were captured and analyzed by a programmed microcomputer for group mean 30-minute fetal heart rate baseline rates and variability and incidences and dimensions of fetal heart rate accelerations and decelerations. Both groups were similar for the maternal and perinatal data examined. The fetal heart rate parameters analyzed were similar within and between each group during each 30-minute testing segment. No episodes of sustained tachycardia or bradycardia were observed. Although 13 fetuses in each group exhibited variable or late decelerations, the incidence of decelerations was no different during periods of rest or ambulation. Maternal ambulation does not elicit abnormal fetal heart rate responses in most high-risk fetuses and may be an acceptable alternative to conventional nonstress test conditions.