Fetal Heart Rate Response Research Articles

The responses to repeated vibroacoustic stimulation in a fetus with trisomy 18

Observation of the fetal movement and fetal heart rate responses to repeated vibroacoustic stimulation might be useful as a measure to assess fetal well-being. Studies of abnormal fetuses are needed to gain insight in the spectrum of possible responses to stimulation. We present a case of a fetus with trisomy 18 that failed to respond to repeated stimulation.

Is intrapartum vibroacoustic stimulation an effective predictor of fetal acidosis?

The hypothesis of this prospective study is that intrapartum vibroacoustic stimulation (VAS) is an effective predictor of fetal acidosis during labor. Various clinical conditions, such as term versus preterm gestation, first stage versus second stage of labor, and fetal heart rate (FHR) variable decelerations versus late decelerations will be tested. During the study period, 113 patients were studied prospectively in either active phase of first stage (n = 53) or during the second stage of labor (n = 60). They were selected from cases exhibiting moderate to severe FHR variable decelerations or late decelerations. The fetuses of study subjects received a VAS for three seconds and FHR changes were recorded. Fetal scalp blood pH or umbilical arterial blood pH was obtained within 15 minutes of VAS. The relationship between FHR responses to VAS and fetal blood pH in term and preterm gestations, the relationship of two tests (VAS and fetal blood pH) to type of FHR decelerations, and the predictability of neonatal morbidity by two tests were analyzed. Where appropriate, Fisher's exact test (p < 0.05 was considered statistically different) and the odd ratio with 95% confidence intervals were used for statistical analyses. Excellent association between acceleration response to VAS and pH > or = 7.20, and between a negative response to VAS (no acceleration or decelerations) and pH < 7.20 were found in the first stage of labor, the second stage of labor, and the combination of both stages together (p = 0.0001, OR = 10.6 [3.3-34.0]). It was observed that negative VAS responses for predicting fetal acidosis (pH < 7.20) were comparable between term (> or = 37 weeks) and preterm (< 37 weeks, > or = 34 weeks) fetuses. Since the preterm fetuses enrolled in the study were limited in number, it is difficult to draw adequate conclusions. The positive predictive value (PPV) of fetal acidosis was 67% in both groups of FHR variable decelerations and late decelerations, but the false negative rate of acceleration VAS response for predicting no acidosis was significantly higher in the group of late decelerations (29% vs 8%, p = 0.034). Finally, both a negative VAS response and fetal acidosis (pH < 7.20) have equal predictability for neonatal morbidity. The PPV of NICU admission by a negative VAS response was two times higher than that of fetal acidosis (PPV = 61% vs 29%, p = 0.038). We found that intrapartum VAS was an effective predictor of fetal acidosis in cases of FHR variable decelerations, but its predictability for fetal acidosis in cases of FHR late decelerations was limited. Both VAS and fetal blood pH are good predictors of neonatal morbidity.

Maximal Exercise Testing in Late Gestation

In Brief Objective To determine the fetal response to and safety of maximal maternal exercise in the third trimester. Methods Twenty-three active women with uncomplicated pregnancies (singleton gestations) underwent maximal exercise testing in late gestation using a progressive maximal cycle ergometer protocol. Fetal heart rate (FHR) responses were monitored and classified using National Institute of Child Health and Human Development guidelines. Statistical analyses involved use of the Student t test, repeated measures analysis of variance with Tukey-Kramer multiple comparisons posttest, and the χ2 test. Results There was an increase in baseline FHR in the 20-minute posttest period compared with the 20-minute pretest period. There were significantly fewer accelerations in the second posttest 10-minute segment compared with the second pretest 10-minute segment. Variability was reduced in both posttest periods compared with the first 10-minute pretest period. Time to reactivity increased after testing. Mild tachycardia was noted in two tracings and bradycardia occurred in a fetus with previously undiagnosed growth restriction. There were no abnormal neonatal outcomes. Conclusion Maximal exercise testing in late gestation led to minimal changes in FHR. Fetal bradycardiac responses were not seen in appropriate for gestational age fetuses, suggesting that brief maximal maternal exertion for research or diagnostic purposes is safe in this group. Fetal responses to maximal exercise testing of healthy women in late gestation were increased fetal heart rate, fewer accelerations, decreased variability, and increased time to reactivity.

Maximal exercise testing in late gestation: fetal responses

Objective: To determine the fetal response to and safety of maximal maternal exercise in the third trimester. Methods: Twenty-three active women with uncomplicated pregnancies (singleton gestations) underwent maximal exercise testing in late gestation using a progressive maximal cycle ergometer protocol. Fetal heart rate (FHR) responses were monitored and classified using National Institute of Child Health and Human Development guidelines. Statistical analyses involved use of the Student t test, repeated measures analysis of variance with Tukey-Kramer multiple comparisons posttest, and the χ 2 test. Results: There was an increase in baseline FHR in the 20-minute posttest period compared with the 20-minute pretest period. There were significantly fewer accelerations in the second posttest 10-minute segment compared with the second pretest 10-minute segment. Variability was reduced in both posttest periods compared with the first 10-minute pretest period. Time to reactivity increased after testing. Mild tachycardia was noted in two tracings and bradycardia occurred in a fetus with previously undiagnosed growth restriction. There were no abnormal neonatal outcomes. Conclusion: Maximal exercise testing in late gestation led to minimal changes in FHR. Fetal bradycardiac responses were not seen in appropriate for gestational age fetuses, suggesting that brief maximal maternal exertion for research or diagnostic purposes is safe in this group.

Computer Analysis of the Fetal Heart Rate

Computer analysis of the fetal heart rate is a technology of the Information Age commercially available for research and clinical practice. Intelligent systems are engineered with algorithms or neural networks designed to simulate expert knowledge. Automated analysis has provided objective, standardized, and reproducible data used to research fetal heart rate responses in the antepartum and intrapartum setting. Perinatal information systems can integrate FHR analysis and data management.

Responses to vibroacoustic stimulation in a fetus with an encephalocele compared to responses of normal fetuses.

Observation of fetal movement and fetal heart rate (FHR) responses to repeated vibroacoustic stimulation (VAS) might be useful as a measure to assess fetal well-being and to assess the integrity of the fetal central nervous system (CNS). We observed the movement and FHR responses to repeated VAS of a term fetus with a serious brain anomaly as compared to responses of normal term fetuses. In 37 normal term fetuses and in a term fetus with an encephalocele we studied movement and FHR response to repeated VAS. All normal fetuses responded within 1 s after stimulation with general body movement and FHR acceleration. At 36 gestational weeks, no movement or FHR responses were seen in the fetus with an encephalocele. Repetition of the test in this fetus after one week still showed no response to repeated VAS. Normal fetuses showed movement and FHR responses to external stimulation. The fetus with an encephalocele did not respond to repeated VAS with a movement or FHR acceleration. Case studies in fetuses with structural anomalies of the CNS are needed to gain insight into the spectrum of possible responses to VAS.

Maternal stress responses and anxiety during pregnancy: Effects on fetal heart rate

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 ± 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color–word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(−)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(−) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(−) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus. © 2000 John Wiley & Sons, Inc. Dev Psychobiol 36: 67–77, 2000

Maternal stress responses and anxiety during pregnancy: Effects on fetal heart rate

This study examined the effect of an acute maternal stress response and anxiety on fetal heart rate. Seventeen healthy, 3rd-trimester pregnant women (mean age = 26 +/- 6 years) were instrumented for continuous electrocardiography, blood pressure (BP), respiration, and fetal heart rate (HR). Subjects completed the state anxiety subscale of the State Trait Personality Inventory (STPI), then rested quietly in a semirecumbent position for a 5-min baseline period, followed by either a 5-min arithmetic or Stroop color-word task. Over the entire 5-min stress period and when averaged across all subjects, the stressors led to significant increases in maternal systolic BP and respiratory rate but changes in maternal HR, diastolic BP, and fetal HR were not significant. However, when subjects were dichotomized into groups that had above or below average anxiety scores [ANX(+) and ANX(-)], both groups had similar respiration rate increases to the stressors, but the BP and fetal heart rate (FHR) responses were significantly different. Women in the ANX(-) group had significantly greater BP responses compared to women in the ANX(+) group whereas the fetuses of ANX(+) women showed significant HR increases and the fetuses of ANX(-) women exhibited nonsignificant decreases. These findings suggest that women's acute emotional reactivity during pregnancy can influence fetal HR patterns and that a stress-induced increase in maternal BP is not the primary signal by which a women's stress response is transduced to her fetus. The results are consistent with the hypothesis that maternal psychological variables may shape the neurobehavioral development of the fetus.

Fetal responses to maternal strength conditioning exercises in late gestation.

Cardiovascular responses to strength conditioning exercises were examined in 12 healthy pregnant women and their unborn fetuses during the third trimester. A group of 12 healthy nonpregnant women of similar ages, parity, body height, and pre-pregnant body mass was also studied. Maternal heart rate and blood pressure and fetal heart rate (FHR) responses were measured in both the supine (30 degrees tilt) and seated postures during handgrip (HG), single-leg extension (SL), and double-leg extension (DL) exercise. Subjects performed 3 sets of 10 reps at 50, 70, and 90% of their 10-repetition maximum (10-RM) for each exercise in both postures. Pregnant subjects exhibited higher heart rates but similar blood pressure responses to control subjects under all experimental conditions. Significant increases were observed for the frequency of FHR accelerations (0.10 to 0.27/min) from rest to DL in the sitting posture at 90% RM. Moderate fetal bradycardia was observed occasionally in the tilted supine posture at rest and both during (SL, DL) and following (HG, SL, DL) exercise, suggesting that this posture should be avoided in late gestation. The results support the safety of moderate strength conditioning exercises in healthy pregnancy.

Physical conditioning effects on fetal heart rate responses to graded maternal exercise.

This study examined the effects of advancing gestational age and maternal aerobic conditioning (stationary cycling) on fetal heart rate (FHR) responses to strenuous non-steady-state maternal exercise. Subjects chose to participate in either an exercise group (EG) or control group (CG). Fourteen healthy, previously sedentary pregnant women participated in the exercise group, and six pregnant controls remained sedentary. Stationary cycling (heart rate target: 145 beats x min(-1)) was performed 3 d x wk(-1) by the exercised group. Exercise duration was increased from 14 to 25 min x session(-1) during the second trimester and was maintained at 25 min x session(-1) throughout the third trimester. FHR was monitored before, during, and after a progressive submaximal cycle ergometer test (peak heart rate = 170 beats x min(-1)) performed at approximately 27 and 37 wk gestation. Mean FHR increased significantly (P < 0.05) during exercise, followed by a modest suppression and then a delayed rise during the recovery period at both observation times. Fetal bradycardia was not observed in any of the exercise tests. Effects of advancing gestational age included a lower FHR baseline both at rest and in response to maternal exercise and a lower incidence of exercise-induced tachycardia. Maternal physical conditioning did not significantly alter FHR response to maternal exercise. Our results support the hypothesis that FHR responses to strenuous exercise are altered by advancing gestational age and a brief progressive exercise test terminated at a maternal heart rate of 170 beats x min(-1) does not induce fetal distress during a healthy pregnancy.

Cardiovascular and metabolic responses to intermittent umbilical cord occlusion in the preterm ovine fetus.

To determine the cardiovascular and metabolic responses to umbilical cord occlusion in the preterm ovine fetus and the impact of repetitive intermittent insults over a 4-day period. Repetitive umbilical cord occlusions (experimental group, n = 7; control group, n = 7) were performed daily (112-115 days' gestation, term = 147 days). Mean arterial pressure (MAP), fetal heart rate (FHR), and FHR variation were monitored, and arterial blood was sampled at predetermined intervals. During umbilical cord occlusions, arterial oxygen pressure (PaO2) (approximately 17 mmHg) and glucose (approximately 0.3) millimoles per liter (mmol/L) fell and arterial carbon dioxide pressure (approximately 8 mmHg) rose (P < .01) to a similar extent on days 1 and 4. Umbilical cord occlusion produced a rise in lactate over the course of successive umbilical cord occlusions each day, the magnitude of which tended to be reduced by day 4 (0.3 +/- 0.1 versus 0.6 +/- 0.1 mmol/L). Control hour FHR and MAP were unaltered over the 4 days, but the delta (delta) FHR to delta PaO2 ratio during umbilical cord occlusions was less on day 4 than on day 1 (6.0 +/- 0.4 versus 10.9 +/- 1.5 beats per minute/mmHg; P < .01). During occlusion hours, high FHR variation episodes, as a measure of fetal activity, were reduced (14.6 +/- 1.5 versus 4.2 +/- 1.3 min/h; P < .01), whereas the reduction in short-term (7.4 +/- 0.7 to 5.8 +/- 0.6 milliseconds; P < .05) and long-term (34.9 +/- 2.7 to 30.0 +/- 0.6 milliseconds; P < .05) FHR variation reached significance only on day 4. The increase in lactate and reduced high-FHR variation episodes over successive umbilical cord occlusions may affect fetal growth and development. Furthermore, repeated umbilical cord occlusions over several days alter the preterm FHR response to subsequent stresses, suggesting an altered chemoreflex response.

Computerised analysis of unstimulated and stimulated behaviour in fetuses with intrauterine growth restriction

Unstimulated (passive) and stimulated behaviour, in the form of fetal heart rate (FHR) and activity (FA)) was studied in 32 normal fetuses and 14 fetuses with intrauterine growth restriction (IUGR). FHR and FA were recorded using a single 1.5 MHz ultrasound transducer and analysed by computer. A 5 s vibroacoustic stimulus (VAS) (electronic artificial larynx) was used for the stimulation studies. The IUGR fetuses had significantly different patterns of both unstimulated and stimulated behaviour compared to normally grown fetuses. When unstimulated they had lower FA rates than the normally grown fetuses but this was only statistically significant at 28–31 weeks. They also spent a significantly lower proportion of time exhibiting high FHR variation at 28–31 weeks. Following VAS the IUGR fetuses had lower FA responses at all gestations and lower FHR responses from 32 weeks, though only the differences in FA response at 28–31 weeks were statistically significant. Of the 14 fetuses with IUGR, all but one exhibited passive behaviour (ERR and/or FA) that was outside the 10–90th range, for normally grown fetuses, whilst 6 of the 14 had responses to VAS that were within the normal range. We do not feel that computerised assessment of stimulated behaviour in preterm IUGR fetuses confers any advantage over passive observations.

Fetal heart rate patterns in term labor vary with sex, gestational age, epidural analgesia, and fetal weight

Objectives: Our purpose was to analyze the previously unreported effect of fetal sex on the fetal heart rate in labor and to measure its magnitude in relation to the effects of other independent clinical variables. Study Design: The last hour of the intrapartum heart rates of 1884 term singleton fetuses collected during routine clinical monitoring over 19 months in Oxford, United Kingdom, was analyzed by computerized techniques. The records were selected for completeness and continuity until within at least 30 minutes of delivery. A subset of records from earlier in labor and a separate archive of antepartum normal term records were also examined. Results: Female fetuses had significantly faster heart rates than male fetuses ( P < .0001). Epidural analgesia, weight percentile (adjusted for age and sex), parity, the duration of first and second stages of labor, and a fall in umbilical arterial blood pH at birth also independently modulated the fetal heart rate (all P < .0001). The effects of these independent variables on heart rate were additive, the most important being epidural analgesia as a cause of tachycardia. The effect of fetal sex was less in the first stage, 6 to 7 hours before delivery, and was not present before the onset of labor (in another 552 pregnancies at 37 to 38 weeks). Conclusions: The fetal heart rate response of female fetuses to normal labor differs from that of male fetuses. Computerized numeric analysis of intrapartum fetal heart rate patterns will need to take into account the multiple factors that influence the fetal heart rate to identify precisely which patterns predict clinical outcome. (Am J Obstet Gynecol 1999;180:181-7.)

The effects of maternal depression on fetal heart rate and fetal heart rate response to vibroacoustic stimulation

The effects of maternal depression on fetal heart rate and fetal heart rate response to vibroacoustic stimulation

Effect of long-term cocaine administration to pregnant ewes on fetal hemodynamics, oxygenation, and growth

To assess uterine and fetal blood flows by Doppler velocimetry and fetal growth and oxygenation in pregnant ewes treated daily with cocaine and to determine whether cocaine impairs fetal cardiac and cerebral reactivity. The study groups received 70 mg (n = 7) or 140 mg (n = 7) of cocaine and the control group (n = 7) received placebo injected intramuscularly daily on days 60-134. Hemodynamic data were measured at rest and during two acute hypoxic tests at cesarean delivery performed on day 134. The fetal heart rate (FHR) and umbilical and uterine resistance indices (RIs) were higher in the cocaine groups than in the control group (FHR: 187 +/- 8 and 166 +/- 8 beats per minute at 83 and 123 days, respectively, in controls and 9-11% higher in cocaine groups; umbilical RI: 0.79 +/- 0.06, 0.60 +/- 0.04, and 0.52 +/- 0.06, at 83, 105, and 123 days, respectively, in controls and 11-17% higher in the cocaine groups [P < .01]; and uterine RI: 0.40 +/- 0.05, 0.40 +/- 0.04, and 0.37 +/- 0.04, at 83, 105, and 123 days, respectively, in controls and 13-35% higher in cocaine groups [P < .05]). At delivery on day 134, the following characteristics were found to be different in the cocaine groups: fetal weight (4.03 +/- 0.2 kg in controls and 15-21% lower in the cocaine groups [P < .02]), partial pressure of oxygen (26.5 +/- 1.4 mmHg in controls and 15-16% lower in cocaine groups [P < .05]), umbilical RI (0.40 +/- 0.03 in controls and 11-17% higher in cocaine groups [P < .01]), cerebral RI (0.61 +/- 0.03 in controls and 9-15% lower in cocaine groups [P < .01]), and cerebral-umbilical ratio (1.52 +/- 0.04 in controls and 22-23% lower in cocaine groups [P < .001]). During the hypoxic tests, the cerebral RI (P < .05) and the cerebral-umbilical ratio (P < .05) decreased significantly less in the two cocaine groups. The FHR response was reduced significantly in the two cocaine groups (P < .05). Long-term exposure to cocaine induces uterine and fetal blood flow disorders, fetal growth restriction, and hypoxia. It reduces the capability of the cerebral vessels to vasodilate and the heart rate to increase during acute hypoxia.

Human Fetal Heart Rate Dishabituation between Thirty and Thirty-Two Weeks Gestation

Few studies of human fetal habituation have included dishabituation procedures (i.e., assessment of the reemergence of a habituated response) to determine if response decrements are the result of reevaluation of information (a brain process) or fatigue of peripheral receptors. The purpose of this study is to describe the ability of the human fetus to learn and recall information with procedures to assess the central nervous system. Fetal heart rate (FHR) of 84 fetuses between 30 and 32 weeks gestational age was examined in response to 3 series of vibroacoustic (VA) stimuli presented at pseudorandom intervals of 25-45 s over the head of the fetus. Responses to the first series of 15 stimuli (S1) were compared with an identical second series of 15 stimuli (S1) presented over the head of the fetus. Between the 2 series, a novel (dishabituating) VA stimulus (S2) was presented, differing from S1 in intensity and frequency. The third series of S1s was applied to the mother's thigh as a control for possible maternal responses to the stimulus. Prestimulus FHR was computed during a 5 s interval before each stimulus, and mean FHR was computed during the intertrial interval (average FHR). The response to S1 during the first series of trials (1-15) produced a sustained rise in both prestimulus and average FHR, r(83) = .90, p < .001. After the novel S2 (trial 16) the rate of change was attenuated for average FHR, r(83) = .12, ns, to S1 for trials 17-31 but not prestimulus FHR, r(83) = .50, p < .001. The decrease in FHR response was reestablished when stimulation was applied to mother's thigh, trials 32-41, r(83) = .92, p < .001. A significant habituation pattern across trials was observed for the first series of S1s when prestimulus HR was subtracted from each preceding average FHR value (delta FHR). After the single novel stimulus (S2), the FHR response to S1 reemerged. All combinations of beginning and ending series slopes were compared, and only the rate of change during the last 4 trials of the initial presentation of S1 and the first 4 trials after the novel stimulus was significant, F(1, 82) = 9.21, p < .003. Uterine contractions collected from the continuous record were not related to the presentation of the novel stimulus, chi 2(1, N = 84) = 0.59, p < .50, ns, or delta FHR slope after the novel stimulus, chi 2(9, N = 84) = 10.52, p < .50, ns. These results established that the 32 week human fetus is capable of detecting, habituating, and dishabituating to an external stimulus and support the premise that areas of the human fetal central nervous system critical for detecting and discriminating information and for learning and memory have developed by the early third trimester.

Fetal heart rate changes do not reflect cardiovascular deterioration during brief repeated umbilical cord occlusions in near-term fetal lambs

OBJECTIVE: Brief repetitive total umbilical cord occlusions were used to induce fetal asphyxia and to evaluate the interrelationships with hypotension and fetal heart rate decelerations. STUDY DESIGN: In 21 chronically instrumented fetal lambs (gestational age 126.8 ± 0.6 days), repetitive total umbilical cord occlusion was performed 1 out of 2.5 minutes (n = 7), 2 out of 5 minutes (n = 9), or not at all (shams, n = 5). Occlusions proceeded until fetal blood pressure was <20 mm Hg or failed to recover to baseline before the next occlusion. RESULTS: At the nadir of asphyxia pH (mean ± SEM) was 6.84 ± 0.02, base excess 23.1 ± 1.0 mmol/L, and lactate 14.2 ± 0.4 mmol/L. Two fetuses died. The pattern of fetal heart rate decelerations remained relatively consistent throughout the experiments. In contrast, after an initial phase of sustained hypertension a progressive fall in trough blood pressure occurred after approximately 15 minutes of occlusion. The blood pressure recovery time in almost all fetuses lengthened abruptly near the end of the occlusion series, at a variable metabolic threshold. This was accompanied by a significant delay in fetal heart rate recovery in only five fetuses. CONCLUSIONS: Fetal compromise presented with the development of hypotension, without change in the pattern of fetal heart rate response. These data illustrate the limited diagnostic value of fetal heart rate monitoring to identify the development of cardiovascular compromise associated with severe decelerations in the previously healthy fetus. (Am J Obstet Gynecol 1997;176:8-17.)

Effects of magnesium sulfate on the fetal heart rate response during acute hypoxemia in goats.

The effects of magnesium sulfate on fetal heart rate (FHR) response during acute hypoxemia in goats were investigated. The FHR responses due to hypoxemia during magnesium sulfate infusion (Mg study) were compared with those during vehicle infusion (controls) in six chronically instrumented goat fetuses at 125-130 days' gestation. Four-hour infusions of magnesium sulfate significantly increased fetal plasma concentrations of magnesium from 2.3 to 6.5 mg/dL. During the hypoxemic period, the fetal arterial oxygen pressure was significantly decreased from 29.0 +/- 2.5 to 14.6 +/- 2.6 torr in the controls, and from 28.9 +/- 3.9 to 13.7 +/- 4.7 torr during the Mg study. Neither arterial carbon dioxide pressure nor pH was significantly altered. In the controls, FHR was significantly decreased by hypoxemia, accompanied by increases in variability. In the Mg study, FHR was not significantly decreased by hypoxemia. Acute hypoxemia also increased the FHR variability during magnesium infusion, which was significantly reduced compared with those in the control population. Magnesium sulfate masks FHR-slowing responses during acute hypoxemia in fetal goats.

Effects of Magnesium Sulfate on the Fetal Heart Rate Response During Acute Hypoxemia in Goats

Effects of Magnesium Sulfate on the Fetal Heart Rate Response During Acute Hypoxemia in Goats

Is intrapartum vibratory acoustic stimulation a valid alternative to fetal scalp pH determination?

To determine the association between fetal heart rate accelerations, whether spontaneous or induced by vibratory acoustic stimulation, and subsequent scalp pH values in presence of a suspicious intrapartum fetal heart rate tracing, and thereby assess the ability of accelerations to predict a concurrent normal fetal scalp blood pH. Prospective observational study of 253 labours involving 421 pH samples. Tertiary care university hospital of Genoeva. Vibratory acoustic stimulation through the maternal abdominal wall for five seconds prior to fetal blood sampling. Spontaneous fetal heart rate reactivity (accelerations) in the 10 min preceding vibratory acoustic stimulation, vibratory acoustic-induced reactivity prior to fetal blood sampling, and scalp pH value. The positive predictive value of a reactive fetal heart rate response after vibratory acoustic stimulation was 78% (95% CI 73-84%) and 97% (95% CI 94-99%) for scalp pH values of > 7.25 and > or = 7.20, respectively. Similar observations occurred with spontaneous reactivity. Of concern, 7 out of 31 (23%) occasions where the scalp blood pH was less than 7.20 appeared to be associated with a normal fetal heart rate response to vibratory acoustic stimulation. Fetal heart rate acceleration induced by vibratory acoustic stimulation was significantly associated with a normal scalp blood pH higher than 7.25. However, vibratory acoustic stimulation offers no advantage over observation of spontaneous fetal heart rate tracings and cannot safely replace fetal blood sampling during labour.