Fetal heart rate and activity patterns in growth-retarded fetuses: changes after vibratory acoustic stimulation.

Seventeen pregnant women who subsequently were delivered of infants with birth weights less than the third percentile were studied for examination of fetal heart rate and fetal activity patterns before and after a 5-second external vibratory acoustic stimulation. None of the fetuses was acidotic at birth. A reduced time was noted during which accelerations in heart rate occurred (50% less) and long-term fetal heart rate variability (25% less) in small for gestational age fetuses compared with age-matched, normally grown fetuses. The incidence of gross fetal body movements was significantly lower (40% less) in small for gestational age fetuses than in those who were appropriate for gestational age. Fetal heart rate and fetal activity patterns after stimulation with the electronic artificial larynx in small for gestational age fetuses were similar to those of appropriate for gestational age fetuses.