Intrapartum assessment of fetal well-being: A comparison of fetal acoustic stimulation with acid-base determinations

Many authorities advocate the use of fetal blood sampling as the final arbiter of abnormal intrapartum fetal heart rate patterns. Alternatively, the presence of an acceleratory fetal heart rate response to scalp stimulation during fetal scalp blood sampling led to the observation that, if present, the likelihood of acidosis was remote. Consequently a prospective intrapartum analysis of evoked accelerations and fetal acid-base status was undertaken. Patients who, on the basis of abnormal fetal heart rate patterns, were judged candidates for acid-base assessment underwent transabdominal acoustic stimulation. The presence or absence of an acceleration was then determined. Sixty-four patients with abnormal intrapartum fetal heart rate patterns underwent intrapartum acoustic stimulation. Thirty fetuses were reactive and all had a pH of ≥7.25. Of the 34 fetuses who were nonreactive, 18 were acidotic. This preliminary observation suggests that acoustic stimulation may be a reasonable clinical alternative to fetal blood sampling when a reactive pattern is observed. In the nonreactive fetuses additional evaluation would appear warranted.