Onset and maturation of fetal heart rate response to the mother's voice over late gestation.

BACKGROUND: Term fetuses discriminate their mother's voice from a female stranger's, suggesting recognition/learning of some property of her voice. Identification of the onset and maturation of the response would increase our understanding of the influence of environmental sounds on the development of sensory abilities and identify the period when speech and language might influence auditory processing. AIM: To characterize the onset and maturation of fetal heart rate response to the mother's voice. METHODS: 143 fetuses from 29 to 40 weeks gestational age (GA) received a standardized protocol: no-sound pre-voice baseline (2 min), audio recording of their mother reading a story (2 min), no-sound post-voice (2 min). The voice was delivered 10 cm above the maternal abdomen at an average of 95 dB A; heart rate was recorded continuously. RESULTS: For data analyses, fetuses were categorized into four age groups: 29­31, 32­34, 35­37, and > 37 weeks GA. Onset of response to the mother's voice occurred at 32­34 weeks GA. From 32 to 37 weeks GA, there was an initial heart rate decrease followed by an increase. At term, there was a response shift to an initial heart rate increase. The percentage of fetuses responding increased over gestation from 46% at 32­34 weeks GA to 83% at term. CONCLUSION: A relatively long latency and sustained duration of the heart rate response suggest auditory processing, the formation of neural networks, above the level of the brainstem.

Maternal heart rate variability and fetal behavior in hypertensive and normotensive pregnancies.

The relation between maternal heart rate variability (HRV) and fetal behavior was examined in hypertensive and normotensive pregnant women. A total of 40 mother-fetal pairs (n = 20 normotensive mothers; n = 20 hypertensive mothers) at 33-41 weeks' gestation were observed using a standardized procedure lasting approximately 50 min. It included the following measurements: maternal beat-by-beat arterial blood pressure and HRV; spontaneous fetal heart rate (HR), body and breathing movements; and an estimate of amniotic fluid volume. The women in the hypertensive group had higher average body mass index (BMI) (33.7 vs. 28.8 kg/m2) than the normotensive group. In the normotensive group, there was no association between maternal HRV and fetal gestational age, HR, body or breathing movements. In the hypertensive group, maternal HRV measures of low-frequency, high-frequency, and total power were associated with fetal gestational age; also, there was an association between maternal autonomic modulation of HR and fetal spontaneous HR. These findings suggest that the maternal autonomic system influences fetal cardiac function in pregnancies complicated by hypertension.

Effects of endotracheal tube suctioning on arterial oxygen tension and heart rate variability.

The purpose of this study was to examine the autonomic mechanisms underlying changes in heart rate (HR) and systolic blood pressure (SBP) responses to endotracheal tube (ETT) suctioning and to compare the open versus closed methods of ETT suctioning on these measures and on arterial oxygen tension. Eighteen orally intubated participants, 33 to 82 years of age (M = 60 years), were randomized for the order of suctioning method. Arterial oxygen tension (PaO2) was measured before suctioning and 30 s and 5 min following suctioning. Beat-to-beat HR and arterial blood pressure data were collected for 10-min periods before and after suctioning. HR and SBP measures were analyzed before suctioning and 1 min and 5 min following suctioning. Although there were no significant effects of ETT suctioning on the autonomic mechanisms of HR modulation and no significant differences between the two methods of suctioning, ETT suctioning resulted in an increase in HR, SBP, and PaO2. However, there was a decrease in the parasympathetic nervous system indicator of HR variability (HRV) following open suctioning. All patients in this study maintained a PaO2 level 80 mm Hg, which may account for our lack of significant autonomic changes. This suggests that hyperoxygenation with 100% oxygen for a minimum of 1 min (or 20 breaths), as delivered by preoxygenation modes available on most microprocessor ventilators, should be the method of choice for all hyperoxygenation procedures to avoid a decrease in PaO2 following suctioning.

Influence of D,L-sotalol on baroreflex sensitivity response to posture following coronary artery bypass graft surgery in men and women.

Low baroreflex sensitivity (BRS) following coronary artery bypass graft (CABG) surgery increases the risk of sympathetically mediated cardiac arrhythmias. To reduce this risk, D,L-sotalol, a nonselective ß-adrenergic receptor antagonist (Class II) and an antiarrhythmic (Class III), is prescribed postoperatively. However, its effect on BRS has not been reported. The purpose of this study was to characterize the influence of D,L-sotalol on BRS measures in supine and standing postures 4 days following CABG surgery. BRS was measured in 27 men and 10 women receiving D,L-sotalol and compared with archival data for 21 men and 10 women obtained prior to the routine administration of D,L-sotalol. In the latter (control) group, 61% had BRS of less than 3 ms/mmHg in the supine posture and 74% in the standing posture compared to 42% with less than 3 ms/mmHg in the supine posture and 65% in the standing posture in the D,L-sotalol group. Men in the D,L-sotalol group showed higher R-R interval and BRS in both supine and standing postures compared with controls. Women in the D,L-sotalol group had higher R-R interval in the supine posture. The higher BRS in men not only reduces the risk of arrhythmias after CABG surgery but may also allow a more rapid circulatory response to the standing posture, thereby decreasing the risk of syncope.

Synergistic effects of low-intensity exercise conditioning and ß-blockade on cardiovascular and autonomic adaptation in pre- and postmenopausal women with hypertension.

The effects of a 12-week low-intensity exercise conditioning program (walking) on blood pressure (BP), heart rate (HR), rate-pressure product (RPP), and cardiac autonomic function were measured in 40 sedentary women with hypertension. Women were assigned to either an exercise group (n = 20) or a control group (n = 20), matched for ß-blockade treatment. They underwent testing at the beginning and at the end of the 12-week study period in three conditions: supine rest, standing, and low-intensity steady state exercise. The exercise group participated in a 12-week, low-intensity walking program, while the control group continued with usual sedentary activity. Compared with the control group, women in the exercise group showed reductions in systolic and diastolic BP and RPP (i.e., the estimated cardiac workload). ß-Blockers increased baroreflex sensitivity and lowered BP and HR in all participants; however, those in the exercise group showed the effects of both treatments: a greater reduction in HR and RPP. The combination of exercise training and ß-blockade produces cardiac and autonomic adaptations that are not observed with either treatment alone, suggesting that ß-blockade enhances the conditioning effects of low-intensity exercise in women with hypertension.

Atypical fetal response to the mother's voice in diabetic compared with overweight pregnancies.

OBJECTIVE: To characterize fetal spontaneous heart rate changes and movements and auditory-elicited heart rate changes in fetuses in diabetic pregnancies compared with those in uneventful, overweight pregnancies. METHODS: Spontaneous heart rate and movements and maternal voice-elicited heart rate changes were observed in 46 mother-fetal pairs (n = 14 gestational diabetic and n = 32 overweight prepregnancy) at 36 (±1) weeks gestational age. Fetal heart rate changes, body movements, and breathing movements were observed for 20 minutes while the mother was at rest. Subsequently, each fetus was presented with a 2-minute audio recording of the mother's voice using the following 6-minute procedure: 2 minutes no-voice baseline, 2 minutes voice presentation, and 2 minutes no-voice postvoice period; heart rate was recorded continuously. RESULTS: There were no differences in spontaneous heart rate changes, body movements, or breathing movements between the 2 groups. Fetuses in the overweight group showed an increase in the heart rate during the playing of their mother's voice, whereas fetuses in the diabetic group showed no response. CONCLUSIONS: Fetuses in overweight pregnancies responded to the mother's voice with an increase in the heart rate as has been reported previously in uneventful pregnancies. The lack of response to the mother's voice in fetuses in diabetic pregnancies may represent immature neural or auditory system development, an increased sensorineural threshold, and thyroid or iron deficiency.

Atypical fetal voice processing in preeclamptic pregnancy.

OBJECTIVE: To compare fetal heart rate (HR) response to the mother's 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 mother's voice when it was played. In comparison, fetuses in the uneventful, normotensive group responded to the mother's voice with a HR increase. CONCLUSION: Fetuses in pregnancies complicated by preeclampsia show atypical auditory processing of the mother's voice. Such atypical responding may reflect a delay in auditory system maturation, functional elevation of sensorineural threshold, or decreased thyroid hormone.

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.

Comparison of fetal behavior in low- and high-risk pregnancies.

Meta-analyses were conducted on archival data of human fetal behavior to identify differential behavior among high-risk fetuses in pregnancies complicated by threatened preterm delivery, maternal hypertension or diabetes compared with low-risk fetuses in uneventful pregnancies, delivering as healthy, full-term infants. Data for a total of 493 fetuses (260 high risk, 233 low risk) from 23 weeks' gestation to term who participated in a study using a standardized protocol including observations of spontaneous and auditory-induced behavior were retrieved from our laboratory database. There were no differences in spontaneous behaviors when scored using clinical criteria for the nonstress test and biophysical profile; however, there were differences in the magnitude of the behaviors measured in the tests. Developmental differences were observed between those threatening to deliver early and the fetuses of hypertensive and diabetic mothers. The latter two groups differed little from one another but differed from low-risk fetuses in their response to auditory stimulation. We concluded that differences in behavior among high-risk groups suggest that atypical fetal behaviors may represent adaptation to condition specific insult rather than a generalized response to insult per se. The finding that high-risk fetuses showed atypical responses to auditory stimuli indicates a need to examine the relation between fetal auditory function and later language acquisition.

Effects of experience on fetal voice recognition.

The ability of human fetuses to recognize their own mother's 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 mother's voice and decreased in response to the stranger's; 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.