Barbara S. Kisilevsky

Effects of Experience on Fetal Voice Recognition

The ability of human fetuses to recognize their own mothers voice was examined. Sixty term fetuses were assigned to one of two conditions during which they were exposed to a tape recording of their mother or a female stranger reading a passage. Voice stimuli were delivered through a loudspeaker held approximately 10 cm above the maternal abdomen and played at an average of 95 dB SPL. Each condition consisted of three 2-min periods: no stimulus, voice (mother or stranger), and no stimulus. Fetal heart rate increased in response to the mothers voice and decreased in response to the strangers; both responses were sustained for 4 min. The finding of differential behavior in response to a familiar versus a novel voice provides evidence that experience influences fetal voice processing. It supports an epigenetic model of speech perception, presuming an interaction between genetic expression of neural development and species-specific experience.

Fetal sensitivity to properties of maternal speech and language

Fetal speech and language abilities were examined in 104 low-risk fetuses at 33-41 weeks gestational age using a familiarization/novelty paradigm. Fetuses were familiarized with a tape recording of either their mother or a female stranger reading the same passage and subsequently presented with a novel speaker or language: Studies (1) & (2) the alternate voice, (3) the fathers voice, and (4) a female stranger speaking in native English or a foreign language (Mandarin); heart rate was recorded continuously. Data analyses revealed a novelty response to the mothers voice and a novel foreign language. An offset response was observed following termination of the fathers and a female strangers voice. These findings provide evidence of fetal attention, memory, and learning of voices and language, indicating that newborn speech/language abilities have their origins before birth. They suggest that neural networks sensitive to properties of the mothers voice and native-language speech are being formed.

Swaddling after heel lance : Age-specific effects on behavioral recovery in preterm infants

We examined responses of preterm infants to swaddling after a heel lance. Fifteen preterm infants from two postconceptional age (PCA) groups (Group 1: n = 7, PCA < 31 wk; Group 2: n = 8, PCA ≥ 31 wk) were observed for 30 minutes during blood sampling followed by routine care; blood sampling followed by swaddling; and no blood sampling and routine care. In both groups, blood sampling resulted in concurrent increases in heart rate and state of arousal, in negative facial displays, and in reductions in blood oxygen-saturation. After the blood was drawn, infants less than 31 weeks PCA exhibited an immediate and spontaneous return to behavioral patterns similar to those observed during the no-blood-sample condition, regardless of treatment condition. Infants 31 weeks PCA or older exhibited protracted behavioral disturbance that was significantly reduced by the use of swaddling. We discuss the significance of these findings.

The effects of exercise conditioning in normal and overweight pregnant women on blood pressure and heart rate variability.

Pre-pregnancy obesity is a risk factor for preeclampsia, gestational diabetes, and hypertension. Regular exercise during pregnancy has been shown to decrease the risk of these obstetrical complications. The purpose of this prospective study was to measure the effects of an exercise program in normal-weight and overweight/obese pregnant women on blood pressure (BP) and cardiac autonomic function, determined by heart rate variability (HRV) and baroreflex sensitivity (BRS). Twenty-two sedentary pregnant women, recruited at 20 weeks gestational age (GA), were grouped as normal weight or overweight/obese. They were systematically assigned to an exercise (walking) group or control (nonwalking) group after the first participants were randomly assigned. Women in the walking groups participated in a 16-week, low-intensity walking program. BP, HRV, and BRS were measured at rest and during exercise at the beginning (20 weeks GA) and end (36 weeks GA) of the walking program. Results indicated that women in the control groups (especially overweight women) showed changes in BP, HRV, and BRS over pregnancy that were not seen in the walking group. Overweight women in the control group increased resting systolic BP by 10 mmHg and diastolic BP by 7 mmHg. HRV declined in the control group but not in the walking group. A reduction in BRS and R-R interval at rest was found in all groups except the walking normal-weight group. The results suggest that an exercise program could attenuate the increase in BP and the loss of parasympathetic tone associated with pregnancy, especially in overweight women.

Fetal Development: Voice Processing in Normotensive and Hypertensive Pregnancies:

Recent observation of maternal voice recognition provides evidence of rudimentary memory and learning in healthy term fetuses. However, such higher order auditory processing has not been examined in the presence of maternal hypertension, which is associated with reduced and/or impaired uteroplacental blood flow. In this study, voice processing was examined in 40 fetuses (gestational ages of 33 to 41 weeks) of hypertensive and normotensive women. Fetuses received 2 min of no sound, 2 min of a tape-recorded story read by their mothers or by a female stranger, and 2 min of no sound while fetal heart rate was recorded. Results demonstrated that fetuses in the normotensive group had heart rate accelerations during the playing of their mothers voice, whereas the response occurred in the hypertensive group following maternal voice offset. Across all fetuses, a greater fetal heart rate change was observed when the amniotic fluid index was above compared to below the median (i.e., 150 mm), indicating that amniotic fluid volume may be an independent moderator of fetal auditory sensitivity. It was concluded that differential fetal responding to the mothers voice in pregnancies complicated by maternal hypertension may reflect functional elevation of sensorineural threshold or a delay in auditory system maturation, signifying functional differences during fetal life or subtle differences in the development of the central nervous system.

Fetuses respond to father's voice but prefer mother's voice after birth

Fetal and newborn responding to audio-recordings of their fathers versus mothers reading a story were examined. At home, fathers read a different story to the fetus each day for 7 days. Subsequently, in the laboratory, continuous fetal heart rate was recorded during a 9 min protocol, including three, 3 min periods: baseline no-sound, voice (mother or father), postvoice no-sound. Following a 20 min delay, the opposite voice was delivered. Newborn head-turning was observed on 20 s trials: three no-sound, three voice (mother or father), three opposite voice, three no-sound trials with the same segment of each parents recording. Fetuses showed a heart rate increase to both voices which was sustained over the voice period. Consistent with prior reports, newborns showed a preference for their mothers but not their fathers voice. The characteristics of voice stimuli that capture fetal attention and elicit a response are yet to be identified.

Human Fetal Responses to Sound as a Function of Stimulus Intensity

&NA; The effect of stimulus intensity on fetal heart rate (FHR) acceleration and body movement responses was evaluated in term fetuses in a two‐stage study. During the first stage (N = 30), a pink noise played at 110 or 105 dB elicited a greater mean peak FHR acceleration than when played at 100 dB. Movement scores indicated that the 110‐dB noise elicited more movements than the 105‐dB noise which, in turn, elicited more than the 100‐dB noise. The FHR acceleration and movement responses elicited on 100‐dB sound trials could not be differentiated from spontaneous activity on no‐sound control trials. During the second stage (N = 93), the 110‐dB pink noise elicited a mean peak FHR acceleration of 14 beats per minute on the first stimulus presentation, replicating the findings of the first stage. Furthermore, the percentage of 110‐dB stimulus/control trials in which there was an FHR acceleration greater than ten beats per minute (stage 1: 57%/10%; stage 2: 58%/24%) and movement response (stage 1: 50%/7%; stage 2: 52%/7%) was virtually identical in the two stages. We conclude that fetal response varies as a function of stimulus intensity and that the threshold for response to an air‐borne pink noise is between 100‐105 dB. These findings have implications for stimulus selection and control procedures in acoustic stimulation testing. (Obstet Gynecol 73:971, 1989)

Fetal sensory-elicited body movements differ in breech compared to cephalic position.

Behavior was examined in 28 near term fetuses in the breech versus cephalic position. Breech fetuses had fewer body movements to a vibroacoustic stimulus and more to an airborne sound. These findings raise the possibility of differential perceptual experience before birth.

Auditory Processing in Growth-Restricted Fetuses and Newborns and Later Language Development

Growth-restricted fetuses and newborns are at increased risk for language deficits, and language impairments have been associated with increased risk for cognitive, social, emotional, and behavioral clinical disorders. Auditory-information processing was examined longitudinally in 167 fetuses in Study 1, 96 of whom were reexamined as newborns in Study 2. In Study 3, language was assessed at 15 months of age for 75 infants from Study 1. Compared with participants who were appropriately grown for gestational age, growth-restricted fetuses showed less sustained response to their mother’s voice; growth-restricted newborns showed less recovery to a novel word after habituation and no preference for their mother’s voice. At 15 months of age, those infants who had been born growth restricted showed expressive-language deficits on Mullen Scales of Early Learning and MacArthur-Bates Communicative Development Inventory subscales. Our results support the hypothesis that fetal growth restriction affects the development of auditory-system functioning and indicate that it may be possible to identify individual fetuses and newborns at risk for language deficits and to intervene early, when the foundation for language is being laid.

Atypical fetal voice processing in preeclamptic pregnancy.

Objective: To compare fetal heart rate (HR) response to the mothers voice in pregnancies complicated by preeclampsia with those of fetuses in uneventful, normotensive pregnancies. Method: Fifty fetuses (n = 22, preeclampsia; n = 28, uneventful, normotensive pregnancies) between 32 and 40 weeks gestational age were recruited. Each fetus was presented with a 2-min no-sound baseline period followed by a 2-min voice period during which an audio recording of his/her mother reading a story was played through a loud speaker over the maternal abdomen at an average of 95 dBA followed by a 2-min no-voice offset period. HR was recorded continuously. Results: Fetuses in the preeclamptic group showed no response to the mothers voice when it was played. In comparison, fetuses in the uneventful, normotensive group responded to the mothers voice with a HR increase. Conclusion: Fetuses in pregnancies complicated by preeclampsia show atypical auditory processing of the mothers voice. Such atypical responding may reflect a delay in auditory system maturation, functional elevation of sensorineural threshold, or decreased thyroid hormone.