In-utero sound levels when vibroacoustic stimulation is applied to the maternal abdomen: an assessment of the possibility of cochlea damage in the fetus

Change in fetal behavior in response to vibroacoustic stimulation

Objective To assess fetal behavioral changes in response to vibroacoustic stimulation (VAS) in normal singleton pregnancies using four-dimensional (4D) ultrasound. Methods Ten types of fetal movements and facial expressions in 68 healthy pregnant women between 24 and 40 weeks were studied using 4D ultrasound for 3 min before and after 3-s VAS. The frequencies of mouthing, yawning, tongue expulsion, back arch, jerky arm movement, startle movement, smiling, scowling, hand-to-face movement, and blinking were evaluated. The fetuses were subdivided into four gestational age groups (24-27, 28-31, 32-35, and ≥36 weeks). Comparison of the frequencies of the fetal behaviors before and after the stimulation in each gestational age group was conducted to detect the response to stimulation with advancing gestation. Results There were no significant differences in the frequency of each fetal behavior before and after VAS at 24-27, 28-31, and 32-35 weeks of gestation. However, the frequencies of blinking and startle movements were significantly higher after VAS in the 36-40 gestational age group (P < 0.05). Conclusion The age of 36 weeks of gestation might represent an advanced stage of brain and central nervous system development and maturation as the response to stimuli is prominent at this age compared with earlier gestation.

Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing

BACKGROUND

Acoustic stimulation of the fetus has been suggested to improve the efficiency of antepartum fetal heart rate testing.

OBJECTIVES

To assess the advantages and disadvantages of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2013).

SELECTION CRITERIA

All published and unpublished randomised controlled trials assessing the merits of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

DATA COLLECTION AND ANALYSIS

All review authors independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information.

MAIN RESULTS

Altogether 12 trials with a total of 6822 participants were included. Fetal vibroacoustic stimulation reduced the incidence of non-reactive antenatal cardiotocography test (nine trials; average risk ratio (RR) 0.62, 95% confidence interval (CI) 0.48 to 0.81). Vibroacoustic stimulation compared with mock stimulation evoked significantly more fetal movements when used in conjunction with fetal heart rate testing (one trial, RR 0.23, 95% CI 0.18 to 0.29).

AUTHORS' CONCLUSIONS

Vibroacoustic stimulation offers benefits by decreasing the incidence of non-reactive cardiotocography and reducing the testing time. Further randomised trials should be encouraged to determine not only the optimum intensity, frequency, duration and position of the vibroacoustic stimulation, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of these stimuli with cardiotocography and other tests of fetal wellbeing.

Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace

BACKGROUND

Fetal vibroacoustic stimulation (VAS) is a simple, non-invasive technique where a device is placed on the maternal abdomen over the region of the fetal head and sound is emitted at a predetermined level for several seconds. It is hypothesised that the resultant startle reflex in the fetus and subsequent fetal heart rate (FHR) acceleration or transient tachycardia following VAS provide reassurance of fetal well-being. This technique has been proposed as a tool to assess fetal well-being in the presence of a nonreassuring cardiotocographic (CTG) trace during the first and second stages of labour.

OBJECTIVES

To evaluate the clinical effectiveness and safety of VAS in the assessment of fetal well-being during labour, compared with mock or no stimulation for women with a singleton pregnancy exhibiting a nonreassuring FHR pattern.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 September 2012) and reference lists of all retrieved articles. We sought unpublished trials and abstracts submitted to major international congresses and contacted expert informants.

SELECTION CRITERIA

All published and unpublished randomised trials that compared maternal and fetal/neonatal/infant outcomes when VAS was used to evaluate fetal status in the presence of a nonreassuring CTG trace during labour, compared with mock or no stimulation.

DATA COLLECTION AND ANALYSIS

Two review authors independently sought to assess for inclusion all the potential studies we identified as a result of the search strategy. We planned to resolve any disagreement through discussion or, if required, to consult a third person. Where there was uncertainty about a particular study, we attempted to contact study authors for additional information. However, these attempts were unsuccessful.

MAIN RESULTS

The search strategies yielded six studies for consideration of inclusion. However, none of these studies fulfilled the requirements for inclusion in this review.

AUTHORS' CONCLUSIONS

There are currently no randomised controlled trials that address the safety and efficacy of VAS used to assess fetal well-being in labour in the presence of a nonreassuring CTG trace. Although VAS has been proposed as a simple, non-invasive tool for assessment of fetal well-being, there is insufficient evidence from randomised trials on which to base recommendations for use of VAS in the evaluation of fetal well-being in labour in the presence of a nonreassuring CTG trace.

Fetal vibroacoustic stimulation in computerized cardiotocographic analysis: the role of short-term variability and approximate entropy

The aim of this study was to evaluate the impact of vibroacoustic stimulation (VAS) on computerized cardiotocography short-term variability (STV) and approximate entropy (ApEn) in both low- and high-risk pregnancies. VAS was performed on 121 high- and 95 low-risk pregnancies after 10 minutes of continuous quiet, while their FHR parameters were monitored and recorded by cCTG analysis. Fetal heart rate was recorded using a computer-assisted equipment. Baseline FHR, accelerations, decelerations, STV, long-term irregularity (LTI), ApEn, and fetal movements (FMs) were calculated for defined observational periods before VAS and after 10 minutes. Data were also investigated in relationship with the perinatal outcome. In each group of patients, FHR after VAS remained almost unmodified. Fetal movements significantly increased after VAS in both groups. Results show that only in the high-risk pregnancies, the increase of STV and the decrease of ApEn after VAS were significantly associated with favorable perinatal outcomes.

Mapping fetal brain development in utero using magnetic resonance imaging: the Big Bang of brain mapping

The development of tools to construct and investigate probabilistic maps of the adult human brain from magnetic resonance imaging (MRI) has led to advances in both basic neuroscience and clinical diagnosis. These tools are increasingly being applied to brain development in adolescence and childhood, and even to neonatal and premature neonatal imaging. Even earlier in development, parallel advances in clinical fetal MRI have led to its growing use as a tool in challenging medical conditions. This has motivated new engineering developments encompassing optimal fast MRI scans and techniques derived from computer vision, the combination of which allows full 3D imaging of the moving fetal brain in utero without sedation. These promise to provide a new and unprecedented window into early human brain growth. This article reviews the developments that have led us to this point, examines the current state of the art in the fields of fast fetal imaging and motion correction, and describes the tools to analyze dynamically changing fetal brain structure. New methods to deal with developmental tissue segmentation and the construction of spatiotemporal atlases are examined, together with techniques to map fetal brain growth patterns.

Neonatal cochlear function: measurement after exposure to acoustic noise during in utero MR imaging

PURPOSE

To establish whether fetal exposure to the operating noise of 1.5-T magnetic resonance (MR) imaging is associated with cochlear injury and subsequent hearing loss in neonates.

MATERIALS AND METHODS

The study was performed with local research ethics committee approval and written informed parental consent. Neonatal hearing test results, including otoacoustic emission (OAE) data, were sought for all neonates delivered in Sheffield who had previously undergone in utero MR imaging between August 1999 and September 2007. The prevalence of hearing impairment in these neonates was determined, with corresponding 95% confidence intervals calculated by using the binomial exact method, and mean OAE measurements were compared with anonymized local audiometric reference data by using the t test.

RESULTS

One hundred three neonates who had undergone in utero MR imaging were identified; 96 of them had completed hearing screening assessment. Thirty-four of these babies were admitted to the neonatal intensive care unit (NICU), and one of them had bilateral hearing impairment. The prevalence of hearing impairment was 1% (one of 96; 95% confidence interval: 0.03%, 5.67%), which is in accordance with the prevalence expected, given the high proportion of babies in this study who had been in the NICU (ie, NICU graduates). In addition, for the well babies, there was no significant difference in mean OAE cochlear response compared with that for a reference data set of more than 16,000 OAE results. When NICU graduates were included in the comparison, a significant difference (P = .002) was found in one of four frequency bands used to analyze the cochlear response; however, this difference was small compared with the normal variation in OAE measurements.

CONCLUSION

The findings in this study provide some evidence that exposure of the fetus to 1.5-T MR imaging during the second and third trimesters of pregnancy is not associated with an increased risk of substantial neonatal hearing impairment.

Using fetal acoustic stimulation to shorten the biophysical profile

PURPOSE

To determine whether fetal acoustic stimulation can decrease the time required to achieve a reassuring biophysical profile.

METHODS

Patients scheduled for a biophysical profile were prospectively assigned to study and control groups. The study group received 3 seconds of acoustic stimulation if fetal breathing, tone, or movement were not present during the first 5 minutes of the study. The biophysical profile was completed in the standard fashion, for both groups.

RESULTS

A total of 870 patients were enrolled (458 control, 412 with stimulation). The fetal acoustic stimulation group had decreased testing time (3 minutes) and fewer non-reassuring tests (5%). The fetal acoustic stimulation group had fewer studies without breathing, potentially reducing the need for further testing or intervention.

CONCLUSIONS

Fetal acoustic stimulation can be used to decrease the biophysical profile testing time and to reduce the number of non-reassuring tests.

Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace

BACKGROUND

Fetal vibroacoustic stimulation is a simple, non-invasive technique where a device is placed on the maternal abdomen over the region of the fetal head and sound is emitted at a predetermined level for several seconds. It is hypothesized that the resultant startle reflex in the fetus and subsequent fetal heart rate acceleration or transient tachycardia following vibroacoustic stimulation provide reassurance of fetal well-being. This technique has been proposed as a tool to assess fetal well-being in the presence of a non-reassuring cardiotocographic trace during the first and second stages of labour.

OBJECTIVES

To evaluate the clinical effectiveness and safety of vibroacoustic stimulation in the assessment of fetal well-being during labour, compared with mock or no stimulation for women with a singleton pregnancy exhibiting a non-reassuring fetal heart rate pattern.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 September 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 1, 2004), MEDLINE (January 1966 to January 2005), EMBASE (January 1966 to January 2005) and reference lists of all retrieved articles. We sought unpublished trials and abstracts submitted to major international congresses and contacted expert informants.

SELECTION CRITERIA

All published and unpublished randomised trials that compared maternal and fetal/neonatal/infant outcomes when vibroacoustic stimulation was used to evaluate fetal status in the presence of a non-reassuring cardiotocographic trace during labour, compared with mock or no stimulation.

DATA COLLECTION AND ANALYSIS

Two independent review authors identified potential studies from the literature search and assessed them for methodological quality and appropriateness of inclusion, using a data extraction form. Attempts to contact study authors for additional information were unsuccessful.

MAIN RESULTS

The search strategies yielded six studies for consideration of inclusion. However, none of these studies fulfilled the requirements for inclusion in this review.

AUTHORS' CONCLUSIONS

There are currently no randomised controlled trials that address the safety and efficacy of vibroacoustic stimulation used to assess fetal well-being in labour in the presence of a non-reassuring cardiotocographic trace. Although vibroacoustic stimulation has been proposed as a simple, non-invasive tool for assessment of fetal well-being, there is insufficient evidence from randomised trials on which to base recommendations for use of vibroacoustic stimulation in the evaluation of fetal well-being in labour in the presence of a non-reassuring cardiotocographic trace.

Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing

BACKGROUND

Acoustic stimulation of the fetus has been suggested to improve the efficiency of antepartum fetal heart rate testing.

OBJECTIVES

The objective of this review was to assess the merits or adverse effects of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register. Date of last search: October 2000.

SELECTION CRITERIA

All published and unpublished randomized controlled trials assessing the merits of the use of fetal vibroacoustic stimulation in conjunction with tests of fetal wellbeing.

DATA COLLECTION AND ANALYSIS

Both reviewers independently extracted data and assessed trial quality. Authors of published and unpublished trials were contacted for further information.

MAIN RESULTS

A total of seven trials with a total of 4325 participants were included. Fetal vibroacoustic stimulation reduced the incidence of non-reactive antenatal cardiotocography test (odds ratio (OR) 0.61, 95% confidence interval (CI) 0.49-0.75) and reduced the overall mean cardiotocography testing time (weighted mean difference (WMD) -4.55 minutes, 95% CI -5.96 minutes to -3.14 minutes). Vibroacoustic stimulation evoked more than mock stimulation when used in conjunction with fetal heart rate testing (OR 0.08, 95% CI 0.06-0.12).

REVIEWER'S CONCLUSIONS

Vibroacoustic stimulation offers benefits by decreasing the incidence of non-reactive cardiotocography and reducing the testing time. Further randomized trials should be encouraged to determine not only the optimum intensity, frequency, duration and position of the vibroacoustic stimulation, but also to evaluate the efficacy, predictive reliability, safety and perinatal outcome of these stimuli with cardiotocography and other tests of fetal wellbeing.

Maternal perception of sound provoked fetal movement for antepartum assessment of fetal well-being

OBJECTIVE

To assess the reliability and application of maternal perception of sound provoked fetal movement for antepartum assessment of fetal well-being.

METHODS

Six hundred singleton high risk pregnant women of at least 32 weeks gestation were studied on 684 occasions. The response was compared with a nonstress test (NST) performed before a 3 second vibroacoustic stimulation with an electronic artificial larynx. The result of maternal perception of sound provoked fetal movement was compared to the NST and the perinatal outcome using sensitivity, specificity, negative predictive value, positive predictive value, and accuracy.

RESULTS

On 684 occasions, a positive response to sound stimulation, recorded as a fetal movement by the mother, occurred on 642 occasions (93.9%) and was accompanied by a reactive NST on 630 occasions; giving a specificity of 97.1% and a negative predictive value of 98.1%. Results of maternal perception of sound provoked fetal movement and NST, performed within a week of delivery, in 560 women were compared with perinatal outcome. The maternal perception of sound provoked fetal movement test had better sensitivity (64.7%) for poor perinatal outcome than the NST (58.8%). Both tests were not different in specificity (96.3% vs 96.5%), positive predictive value (35.5% vs 34.5%), negative predictive value (98.9% vs 98.7%), and accuracy (95.4% vs 95.4%).

CONCLUSION

The findings suggested that maternal perception of sound provoked fetal movement may be an effective screening test to identify fetal compromise in antepartum period. This test is a simple and inexpensive test for evaluating fetal well-being in primary health care setting.

Heart rate changes following habituation testing of the motor response in normal human fetuses

We examined the heart rate (HR) response immediately following habituation testing in 54 normal human fetuses between 34 and 40 weeks of gestation to determine if cardiac self-regulation was a function of the rate of motor habituation. All fetuses received eight trials of a 1-s vibroacoustic stimulus (VAS) with a 10-s interstimulus interval. A score of 0-10 was assigned for each trial based on subjective assessment of intensity and duration of the fetal motor response. Motor habituation was evaluated in terms of the rate of response decrement over trials. For each fetus the average post-VAS HR was calculated in 1-min blocks for the first 7 min following habituation testing. When subjects were divided into slow and fast motor habituators, we found that fetuses who were slow habituators displayed a significantly greater increase in HR above baseline at each of the first 7 min following habituation testing as compared to fetuses whose motor response habituated more rapidly, F(1,52) = 4.88, P = 0.03. However, there was no difference between slow and fast motor habituators in the rate at which the HR returned toward prestimulus levels. To further examine these results, we divided the 54 fetuses into four groups based on the medians of the slope of the post-VAS HR regression line and the variability in HR about this line. We found that fetuses whose HR decreased slowly after habituation testing displayed significantly greater variability in their cardiac response as compared to fetuses whose HR decreased more rapidly (chi 2 = 4.74, P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)