Differential effects of prenatal rhythmic stimulation on neonatal arousal states.

This study tested Salk's hypothesis that the human fetus is prenatally imprinted to the repetitive intermittent sound of the maternal heartbeat. 2 groups of neonates were selected prior to birth based on low (70-80 bpm) and high (100-110 bpm) maternal resting heart rates. At 24-48 hours old, the neonates were exposed to a 75-bpm, 105-bpm, or a no-sound tape, each prior to 1 of 3 different mealtimes. The prediction, based on Salk's hypothesis, that neonates would quiet most to their own mother's heart rate compared with the unfamiliar heart rate was not supported. Greater arousal reduction was found for any rhythmic sound compared with no sound. M-st important, clear prenatal influences on postnatal quieting behavior were demonstrated. Babies born to low-heart-rate mothers fell asleep faster, slept longer, and cried less under all conditions than did high-maternal-heart-rate children.