Fetal heart rate response to a controlled sound stimulus as a measure of fetal well-being.

The fetal heart rate (FHR) response to a controlled sound stimulus of 80 dB was registered in 152 at-risk pregnancies. Thirty-four of the infants showed signs of an intra-uterine pathological condition at birth, whereas 118 infants were clinically unaffected. The mean heart rate response was significantly weaker in the pathological group than in the normal group. A FHR response of less than 15 bpm was found to give a test sensitivity of 53%. The differences between the two groups revealed by the sound stimulation test corresponded to differences in birth weights and in Apgar score after 1 minute. The results indicate that the sound stimulation test is sensitive to minor changes in the condition of the fetus.