Fetal heart rate response to controlled sound stimuli during the third trimester of normal pregnancy.

Fetal heart rate (FHR) responses to controlled sound stimuli were compared in the 32nd, 35th and 39th week of pregnancy. Though a tendency to a greater FHR response to sound was found as gestation advanced, this increase would seem to be so small that it may be ignored in practice. The earlier demonstrated influence of stimulus intensity and prestimulus heart rate level on the FHR response to sound were confirmed.