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Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing

  1. Kelvin H Tan1,*,
  2. Rebecca MD Smyth2,
  3. Xing Wei1

Editorial Group: Cochrane Pregnancy and Childbirth Group

Published Online: 7 DEC 2013

Assessed as up-to-date: 30 SEP 2013

DOI: 10.1002/14651858.CD002963.pub2


How to Cite

Tan KH, Smyth RMD, Wei X. Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing. Cochrane Database of Systematic Reviews 2013, Issue 12. Art. No.: CD002963. DOI: 10.1002/14651858.CD002963.pub2.

Author Information

  1. 1

    KK Women's and Children's Hospital, Department of Maternal Fetal Medicine, Singapore, Singapore

  2. 2

    The University of Manchester, School of Nursing, Midwifery and Social Work, Manchester, UK

*Kelvin H Tan, Department of Maternal Fetal Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore, 229899, Singapore. khtan@tan.net. tan.kok.hian@kkh.com.sg.

Publication History

  1. Publication Status: New search for studies and content updated (no change to conclusions)
  2. Published Online: 7 DEC 2013

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Characteristics of included studies [ordered by study ID]
Bolnick 2006

MethodsComputer-generated randomisation schedule.


ParticipantsThe study population consisted of patients at 33 to 39 weeks of gestation who underwent an NST. Excluded were cases in which the fetus had a cardiac or central nervous system anomaly or had been exposed to a maternal drug that affected the central nervous system or FHR beat-to-beat variability.


InterventionsAssigned to receive transabdominal light, vibroacoustic, or no stimulation. The order in which each pregnancy was assigned to receive transabdominal light, vibroacoustic, or no stimulation was determined before the first of the 3 tests according to a computer-generated randomisation schedule. The minimum period between tests was 3 days.The 2 investigators who interpreted each tracing were blinded as to the type of stimulation.


OutcomesPrimary outcome: FHR reactivity. An adequate FHR acceleration was defined as 15 bpm above baseline for 15 seconds. If it was absent, the stimulus was repeated 10 minutes later up to a maximum of 3 times during the 20-minute NST. Primary endpoints for comparison were the time from the onset of stimulation until the first adequate FHR acceleration and the time before a reactive pattern (2 adequate accelerations).


Notes


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskComputer-generated randomisation schedule.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNot documented if participant or caregiver blinded. 2 outcome investigators who interpreted each tracing were blinded.

Incomplete outcome data (attrition bias)
All outcomes
Unclear risk11 cases discontinued the trial before completion of NST and data not analysed.

Selective reporting (reporting bias)Unclear riskNo outcomes documented in methods section.

Other biasLow riskNo evidence of any other form of bias.

Marden 1997

MethodsRandomisation: randomised by sealed envelopes with the use of a statistical package to generate the sequence of assignment.


ParticipantsWomen of at least 31 weeks' gestation. Inclusion criteria included singleton pregnancy, intact membranes, and no concurrent use of magnesium or narcotics. Country: USA, Colorado. 577 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were given acoustic stimulation for 3 seconds with the stimulator placed at the midpoint between the maternal pubic symphysis and umbilicus. Fetal movements were palpated with the other hand at the fundus. Women randomised to control group were given mock stimulation for 3 seconds with the stimulator placed at the midpoint between the maternal pubic symphysis and umbilicus. Fetal movements were palpated with the other hand at the fundus.


OutcomesPrimary outcome: positive test as defined by palpation or visualisation of fetal movement only by the tester during a vibroacoustic stimulation.
Other outcome: FHR reactivity.


NotesThe vibratory acoustic stimulus was performed using a vibroacoustic stimulator (Corometrics 146 fetal acoustic stimulator). Randomisation was performed after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandomisation with the use of a statistical package to generate the sequence of assignment.

Allocation concealment (selection bias)Low riskSealed envelopes.

Blinding (performance bias and detection bias)
All outcomes
Low riskBy performing the fetal acoustic stimulation test before NST, the tester was blinded to the result of NST.

Incomplete outcome data (attrition bias)
All outcomes
Unclear riskFor 23 women, outcome data were not available. No further information provided.

Selective reporting (reporting bias)Unclear riskNo outcomes documented in methods section.

Other biasLow riskNo evidence of any other form of bias.

Marquez 1993

MethodsRandomisation: randomised by lottery. Effectiveness of randomisation was assessed by comparisons of several parameters within the two groups which included gestational ages and primary indications.


ParticipantsWomen of least 32 weeks' gestation. Country: Mexico. 180 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were given acoustic stimulation for 5 seconds.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations or more of greater than 15 bpm and of 15 seconds duration or more within a 10-minute period.


NotesStimulus had an audio frequency of 75 Hz and intensity of 74 db and a stimulation duration of 5 seconds. Randomisation was done after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandom selection.

Allocation concealment (selection bias)Low riskSealed envelopes.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskOutcome assessor blinded to treatment group.

Incomplete outcome data (attrition bias)
All outcomes
Unclear riskUnable to assess.

Selective reporting (reporting bias)Unclear riskUnable to assess.

Other biasUnclear riskUnable to assess.

Newnham 1990

MethodsRandomisation: randomised by draw of sealed envelopes. Effectiveness of randomisation was assessed by comparisons of several parameters within the 2 groups which included maternal ages, parities, gestational ages and primary indications.


ParticipantsWomen of least 34 weeks' gestation. Exclusion criteria - no contraindications to contraction stress tests. Country: Western Australia. 172 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were monitored for an initial 5 minutes. If the pattern is non-reactive, a 3-second vibratory acoustic stimulation was applied to the maternal abdomen in the region of the fetal head. The stimulus was repeated a second and a third time, also at 1-minute intervals, if satisfactory FHR accelerations had not occurred.
Women randomised to non-fetal acoustic stimulation group were monitored for an initial 20 minutes. If the trace was non-reactive, the fetus was stimulated manually and the test was continued for a further 20 minutes. If satisfactory accelerations were not found, the women were then sent for a meal. On her return, a nipple stimulation contraction stress was performed if the subsequent test remained non-reactive after a further 20 minutes.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations of greater than 15 bpm and of 15 seconds' duration or more within a 20-minute period. In tests in which accelerations had been provoked by fetal acoustic stimulation, the definition of reactivity required 1 of the 2 accelerations to have been unprovoked.


NotesAll tests were performed with Corometrics 115 monitors using Doppler FHR transducers. The tests were performed by specially trained fetal intensive care midwives with a nurse: patient ratio of 1:1. The vibratory acoustic stimulus had an audio frequency of 75 Hz, a sound intensity of 74 db at 1 m in air and a stimulation duration of 3 seconds. Randomisation was performed after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandomisation by draw of sealed envelopes.

Allocation concealment (selection bias)Low riskSealed envelopes.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNo evidence of blinding.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up 100%.

Selective reporting (reporting bias)Unclear riskNo outcomes documented in methods section.

Other biasLow riskNo evidence of any other form of bias.

Papadopoulos 2007

MethodsRandomisation was done with the use of a random number generator in the computer.


ParticipantsThe population of the study consisted of patients referred for fetal surveillance to the maternal-fetal medicine department (either on an outpatient basis or after admission to the hospital for various reasons). Inclusion criteria were: singleton pregnancy, gestational age equal or more than 30 weeks + 0 day and BPPS ≤ 8/10 with a non-reactive NST. Exclusion criteria were: gestational age before 30 weeks, multifetal pregnancy, premature rupture of membranes, known congenital anomalies of the fetus and maternal refuse to participate in the study.


InterventionsThe patients were followed according to department’s protocol, and biophysical profile was conducted for 30 minutes according to standard criteria. All participants with an abnormal or equivocal BPPS were assigned randomly to 1 of 2 groups. In group A (study group), VAS was applied and, in group B (control group), the observation time was extended. In group A, a 3-second duration stimulus was applied with an artificial larynx placed on maternal abdomen over the fetal vertex. Following VAS, BPPS was reassessed for 30 minutes and if remained non-reassuring a second 3-second stimulus was applied. BPPS was assessed again for another 30 minutes. In group B, we followed the classical method of extended observation time for 60 minutes, divided into 2 periods of 30 minutes each to match the time periods of group A. Participants of both groups with a non-reassuring BPPS at the end of the examination were managed accordingly. BPPS with or more than 8/10 with a reactive NST at any stage was considered indicative of a non-compromised fetus.


OutcomesIntrauterine death, caesarean section for fetal distress, Apgar score at 5 minutes, meconium-stained amniotic fluid, admission to NICU for whatever reason.


Notes


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandom number generator in the computer.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
High riskNot performed.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Low riskAll outcomes in the methods section have been reported on in the results section.

Other biasLow riskNo evidence of any other form of bias. 

Perez-Delboy 2002

MethodsRandomisation: randomisation method unknown.


ParticipantsWomen referred to antenatal testing unit for NST.
Country: New York, USA.
113 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were given 1 second vibroacoustic stimulation at the maternal abdomen. The stimulus was repeated a second (for 2 seconds) and a third time (for 3 seconds), also at 10-minute intervals, if still not reactive.
Women randomised to non-fetal acoustic stimulation group were given the traditional NST without the vibroacoustic stimulation.


OutcomesPrimary outcome: FHR reactivity.


Notes


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear riskRandomisation method unknown.

Allocation concealment (selection bias)Unclear riskNo information provided.

Blinding (performance bias and detection bias)
All outcomes
Low riskOutcome assessor blinded.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Unclear riskNo outcomes documented in methods section.

Other biasUnclear riskUnable to assess.

Salamalekis 1995

MethodsRandomisation: randomisation method unknown. Effectiveness of randomisation was assessed by comparisons of parities. There was no statistical significant difference.


ParticipantsWomen of least 37 weeks' gestation with singleton and high risk pregnancies. Country: Greece. 225 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were monitored for at least 5 minutes. A vibratory acoustic stimulation was applied to the maternal abdomen in the region of the fetal head and activated for 1 second 4 consecutive times, with 1 second intervals between stimulations.
Women randomised to non-fetal acoustic stimulation group were monitored for an initial 20 minutes. If the trace was non-reactive, the test was continued for a further 20 minutes.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations of 15 bpm and of at least 15 seconds' duration or a FHR acceleration of 15 bpm over the baseline for 2 minutes within 5 minutes after acoustic stimulation. Non-reactivity was defined as 40 minutes without a single FHR acceleration of 15 bpm or more, for 15 seconds or more.
Other outcome: fetal distress within 7 days of test. This was defined by the presence of pathological FHR trace pattern, thick meconium or low Apgar at 5 minutes.


NotesAll tests were performed with Corometrics 115 monitors. The tests were performed 1 hour after a meal in a low noise room with the mother in a semi-recumbent position to minimise the risk of supine hypotension. The vibratory acoustic stimulus was performed using a vibroacoustic stimulator (Corometrics 146 fetal acoustic stimulator), with a sound intensity of 110 db in air. Randomisation after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear riskAllocated at random.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
High riskNot performed.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Low riskAll outcomes in the methods section have been reported on.

Other biasLow riskNo evidence of any other form of bias.

Saracoglu 1999

MethodsRandomisation: randomisation method unknown.


ParticipantsWomen seen at Perinatology Unit.
Country: Turkey.
400 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were monitored for at least 5 minutes. A vibratory acoustic stimulation was applied to the maternal abdomen in the region of the fetal head and activated for 1 second up to 4 times.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations of 15 bpm and of at least 15 seconds' duration within a 20-minute period. Non-reactivity was defined as 40 minutes without the reactive criterion.


NotesA fetal acoustic stimulator (Model 146; Corometrics, Wallingford, CT;75 Hz, 74 db) was used, and FHR was recorded with a fetal heart monitor (Model 115; Corometrics).

The report by Saracoglu 1998 only provided data in abstract form and these were inadequate. There was no reply despite various attempts to contact the authors. The abstract was subsequently published in full (Saracoglu 1999) and the published paper (Saracoglu 1999) is included in this review.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)High risk The study participants were randomly selected from patients applying to the unit. However, the assignment to acoustic stimulation or NST does not appear to be randomised ("divided equally").

Allocation concealment (selection bias)Unclear riskNo information provided.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNo information provided.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Low riskAll outcomes in the methods section have been reported on.

Other biasUnclear riskNo information provided.

Sleutel 1990

MethodsRandomisation: randomised by means of a random number table.


Participants60 pregnant women at a university hospital who were scheduled for NST. Exclusion criteria were gestational age less than 30 weeks, abnormal FHR, non-reactive NST or a positive contraction at the last antepartum evaluation, mothers who appeared sedated or had used narcotics, sedatives or street drugs within 8 hours and termination of testing on the mother or fetus before completion of NST. Country: USA, Utah.


InterventionsThey were randomised to 3 groups (control, single stimulation and intermittent stimulation). Women randomised to control group received the traditional NST. Women randomised to the single fetal acoustic stimulation group were given acoustic stimulation for a single 5-second duration with the artificial larynx placed at the maternal abdomen over the fetal head. Women randomised to the intermittent fetal acoustic stimulation group were given acoustic stimulation for 4 3-second duration with the artificial larynx placed at the maternal abdomen over the fetal head. Each stimulus was separated by 2 minutes.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations of 15 bpm and of at least 15 seconds' duration within a 20-minute period. Non-reactivity was defined as 90 minutes without the reactive criterion.


NotesThe vibratory acoustic stimulus was performed using a hand held artificial larynx with a sound pressure level in air of 100 db at 1000 Hz. Randomisation was performed after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandom number table was used.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNo information provided.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Low risk2 hypotheses were stated in the methods section and both were tested.

Other biasLow riskNo evidence of any other form of bias.

Smith 1986

MethodsRandomisation: randomised by lottery. Effectiveness of randomisation was assessed by comparisons of several parameters within the 2 groups which included parities, gestational ages and primary indications.
It was noted that there was a significantly greater number of postdates women in the non-fetal acoustic stimulation group.


ParticipantsWomen of at least 28 weeks' gestation presenting to the Antepartum Fetal Testing Unit of the Hospital. Exclusion criteria - none. Country: USA, California. 715 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were monitored for an initial 5 minutes. If the pattern is non-reactive, a 3 second or less vibratory acoustic stimulation was applied to the maternal abdomen in the region of the fetal head. The stimulus was repeated for a maximum of 3 times, at 1-minute intervals, if satisfactory FHR accelerations had not occurred.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 accelerations or more of greater than 15 bpm and of 15 seconds' duration or more within a 10-minute period. Non-reactivity was defined as 40 minutes without 2 qualifying accelerations.


NotesAll acoustic tests were done with a Model 5C electronic artificial larynx (Western Electric, New York) and performed in the Antepartum Fetal Testing Unit by specially trained nurses with the woman in semi-Fowler's position. Sound pressure levels of this device measured at 1 m in air averaged 82 db, with a fundamental frequency of approximately 80 Hz, and harmonics ranging from 20 to 9000 Hz. Randomisation was done after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandomised by lottery.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskUnclear.

Incomplete outcome data (attrition bias)
All outcomes
Low riskNo patients were excluded. Those who refused participation served as a second control group.

Selective reporting (reporting bias)Low riskAll outcomes in the methods section have been reported on.

Other biasUnclear riskUnclear.

Sood 2007

MethodsRandomly allocated by computer-generated random numbers kept in sealed envelopes to either vibroacoustic stimulated modified biophysical profile (VAS/mFBP) or mock stimulation (mFBP).


Participants214 women with high risk singleton pregnancies detected amongst women attending antenatal clinic. Country: India.


InterventionsVibroacoustic stimulation was done with EMCO vibroacoustic stimulator (EMCO Health Care Pvt Ltd, Sion, Mumbai, India) with 75 db sound intensity at 1.0 meter and frequency of 75 Hz.


OutcomesMean testing time for modified biophysical profile, caesarean section for fetal distress, 5 minute Apgar score < 7, admission to NICU for more than 24 hours.


Notes


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskRandomised by computer-generated random numbers.

Allocation concealment (selection bias)Low riskRandom numbers kept in sealed envelopes.

Blinding (performance bias and detection bias)
All outcomes
Unclear riskUnclear.

Incomplete outcome data (attrition bias)
All outcomes
Low riskFollow-up: 100%.

Selective reporting (reporting bias)Low riskAll outcomes in the methods section have been reported on in the results section.

Other biasLow riskNo evidence of any other form of bias.

Tongsong 1994

MethodsRandomisation: randomisation method unknown. Effectiveness of randomisation was assessed by comparisons of several parameters within the 2 groups which include maternal ages, gestational ages and primary indications. All the FHR tracings were interpreted blindly by 1 independent perinatologist, who did not have any clinical information on the group of women.


ParticipantsWomen of least 28 weeks' gestation with indications including postterm pregnancy, intrauterine growth retardation, pregnancy-induced hypertension, chronic hypertension, decreased fetal movement and diabetes mellitus. Country: Thailand. 1273 women randomised.


InterventionsWomen randomised to fetal acoustic stimulation group were given fetal acoustic stimulation for 1 second. If no qualifying acceleration was observed within 15 seconds, the stimulus were repeated up to 3 times. If reactive criteria were not achieved in 10 minutes, a new cycle of stimulation was begun. If both the women in the acoustic stimulation and standard non-acoustic stimulation groups did not meet the reactive criteria within 20 minutes of the tests, the same technique was extended another 20 minutes.


OutcomesPrimary outcome: FHR reactivity. This was defined by the presence of 2 FHR accelerations or more of greater than 15 bpm and of 15 seconds' duration within a 20-minute period. 1 prolonged acceleration of the FHR of at least 15 bpm lasting more than 2 minutes was also interpreted as reactive. If these criteria were not met in 40 minutes of monitoring, the test was interpreted as non-reactive.


NotesAll acoustic tests were performed in the Maternal Fetal Medicine Unit by a specially trained physician with the woman in semi-Fowler's position. Transabdominal acoustic stimulation overlying the fetal vertex was accomplished with an electronic fetal larynx of approximately 80 db and frequency of 80 Hz and a stimulation duration of 1 second. Randomisation was done after informed consent.


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear riskRandomisation method unknown.

Allocation concealment (selection bias)Unclear riskUnclear.

Blinding (performance bias and detection bias)
All outcomes
Low riskAll the FHR tracings were interpreted blindly by one independent perinatologist, who did not have any clinical information on the group of women.

Incomplete outcome data (attrition bias)
All outcomes
Unclear riskUnclear.

Selective reporting (reporting bias)Unclear riskUnclear.

Other biasUnclear riskUnclear.

 
Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Berclaz 1991There was a discrepancy between the number of participants presented in figure 3 (n = 18 for sham and n = 16 for real stimulation) and that stated in the text (n = 25). The definition of quiet and active fetuses was not clear. There were 2 types of bars representing tranquille (quiet) fetuses with different shades but no legend was given.

Devoe 1989Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Eller 1992Pseudo-randomisation performed using hospital odd or even number. There was a large difference between those given vibroacoustic stimulation over the fetal vertex (n = 115) and over fetal breech (n = 90). There was also discrepancy between the total numbers presented for the results relating to reactive tests (the fetal vertex (n = 96) and over fetal breech (n = 55).

Gagnon 1986Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Gagnon 1987Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Gagnon 1988Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Gonzalez 1998Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Groome 1993Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Groome 1994Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Hamner 1988Data only available in abstract form and were inadequate. There was an unexplained discrepancy between the control (n = 286) and vibroacoustic stimulation (n = 135) groups.

Hasanpour 2013Not eligible as study compared acoustic stimulation and feeding mother stimulation.

Kisilevsky 1990Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Kisilevsky 1992Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Maesel 1994Data were not presented or available, or extractable as the specified clinical outcome measures for this review.

Montan 1992aData were not presented or available, or extractable as the specified clinical outcome measures for this review.

Montan 1992bData were not presented or available, or extractable as the specified clinical outcome measures for this review.

Petrovic 1998The control group (n = 326) was larger than the study group (n = 168). The control group had 2 distinct groups of which 1 group consisted of 158 women with evident fetal activity at the onset after the initial randomisation by schedule and the second group comprised 168 women after randomisation with no distinct fetal heart activity. These 2 distinct groups are analysed together as the control group. Analyses of the results of the 2 groups separately were not available.

Pinette 2005Quasi-randomisation performed using hospital odd or even number.

Schiff 1992The results of the experimental group were compared to a big group (both experimental and control) and presented. Results relating to the control group alone were not available and not extractable.

Smith 1988The women were randomised but only women delivering within 7 days of a reactive cardiotocograph test were reported. There were 314 women in the control group and only 227 women in the study group. There is also a higher incidence of postdatism in the control group.

 
Characteristics of studies awaiting assessment [ordered by study ID]
Gonzalez 1995

Methods

Participants

Interventions

Outcomes

NotesArticle in Spanish - awaiting translation

 
Comparison 1. Fetal vibroacoustic stimulation versus mock or no stimulation

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Non reactive cardiotocography test94817Risk Ratio (M-H, Random, 95% CI)0.62 [0.48, 0.81]

 2 Mean overall fetal heart rate testing time32295Mean Difference (IV, Random, 95% CI)-6.93 [-12.09, -1.76]

 3 Absence of fetal movements by palpation or visualisation1577Risk Ratio (M-H, Fixed, 95% CI)0.23 [0.18, 0.29]

 4 Fetal distress within 7 days2434Risk Ratio (M-H, Fixed, 95% CI)1.00 [0.62, 1.60]

 5 False positive in prediction of fetal distress within 7 days3747Risk Ratio (M-H, Fixed, 95% CI)0.49 [0.26, 0.92]

 6 False negative in prediction of fetal distress within 7 days387Risk Ratio (M-H, Fixed, 95% CI)0.82 [0.49, 1.40]

 7 Perinatal deaths54107Risk Ratio (M-H, Fixed, 95% CI)0.98 [0.46, 2.10]

 8 Impairment of fetal hearing1120Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

9 Impairment of neurological development00Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

10 Maternal anxiety00Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

11 Maternal satisfaction00Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

 12 Mean testing time for modified biophysical profile - not prespecified outcome1214Mean Difference (IV, Fixed, 95% CI)-2.85 [-3.14, -2.56]

 13 Non-reassuring biophysical profile - not prespecified outcome12833Risk Ratio (M-H, Fixed, 95% CI)0.71 [0.52, 0.97]

 
Comparison 2. Fetal vibroacoustic stimulation versus mock stimulation

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Non reactive cardiotocography test2791Risk Ratio (M-H, Fixed, 95% CI)0.80 [0.43, 1.51]

 2 Absence of fetal movements by palpation or visualisation1577Risk Ratio (M-H, Fixed, 95% CI)0.23 [0.18, 0.29]

 3 Mean testing time for modified biophysical profile1214Mean Difference (IV, Fixed, 95% CI)-2.85 [-3.14, -2.56]

 4 Fetal distress within 7 days1214Risk Ratio (M-H, Fixed, 95% CI)0.54 [0.16, 1.79]

 5 False positive in prediction of fetal distress within 7 days1203Risk Ratio (M-H, Fixed, 95% CI)0.18 [0.01, 3.77]

 6 False negative in prediction of fetal distress within 7 days111Risk Ratio (M-H, Fixed, 95% CI)0.88 [0.11, 6.88]

 7 Perinatal deaths1214Risk Ratio (M-H, Fixed, 95% CI)0.63 [0.11, 3.70]

 
Comparison 3. Fetal vibroacoustic stimulation versus manual stimulation

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Non-reactive cardiotocography1300Risk Ratio (M-H, Fixed, 95% CI)0.68 [0.38, 1.21]

 2 Need for contraction stress test1300Risk Ratio (M-H, Fixed, 95% CI)0.38 [0.10, 1.39]

 3 Perinatal deaths1172Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

 
Comparison 4. Intermittent vibroacoustic stimulation versus single vibroacoustic stimulation

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Mean testing time for reactive tests145Mean Difference (IV, Fixed, 95% CI)0.30 [-1.27, 1.87]

 
Comparison 5. Fetal vibroacoustic stimulation versus light stimulation

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Non-reactive cardiotocography test1120Risk Ratio (M-H, Fixed, 95% CI)0.5 [0.05, 5.37]

 2 Perinatal deaths1120Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

 3 Impairment of fetal hearing1120Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]