We have previously demonstrated that premature neonates (34-38 gestational weeks) react differently to their mother's addressed voice than to adult directed speech. Their heart rate variability is lowered, and the mean frequency increases or decreases according to the neonate's prior behavioral state. Similarly fetuses (36-39 gestational weeks) have been given their mother's voice during 4 minutes each, separated by 3 minutes of silence: 1)reading a text; 2)talking to them; 3)talking to an adult, then: 4)her recorded “talking to them” in broadcasted above the abdomen and also: 5)a standard sound (ocean waves). The signal of fetal heart rate pattern is obtained from a Hewlett-Packard 8040 fetal monitor interfaced to an IBM-PC compatible computer. Spectral analysis was performed every 51.2 seconds on each recording, and comprised the measurement of spectral density (SD) every 0.02 Hz, as well as the determination of the position of the maximum energy peak (PMEP). In the 0.02-0.05, 0.05-0.15 and 0.15-0.5 Hz bands.

Results show that the mother's addressed speech usually decreases the FHR frequency as well as it variability. These variations are influenced by:

  • prior fetal behavioral status.

  • the presence or absence of mother's habitual vocal interactions with her fetus.

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