Fetal Acoustic Stimulation Research Articles

Should assessment of amniotic fluid volume form an integral part of antenatal fetal surveillance of high risk pregnancy?

This study was conducted to evaluate the role of the Amniotic Fluid Index (AFI), used along with nonstress cardiotocography (NST) and fetal acoustic stimulation test (FAST), when required, in prediction of adverse pregnancy outcome. Over a 3-year period 565 pregnant women had antepartum fetal surveillance due to various high risk pregnancy factors and delivered within 7 days of the test. Antepartum fetal surveillance included nonstress cardiotocography together with estimation of AFI. Need for induction of labour, presence of meconium at rupture of membranes, Caesarean section for fetal distress, Apgar score at 5 minutes, need for neonatal endotracheal intubation, admission to neonatal special care unit and perinatal death were the main outcome measures. Nonreactive nonstress tests and Caesarean sections for fetal distress were more common and neonatal outcome was significantly poorer in patients with AFI < 5 cm than in those with higher AFI values. Of the 4 perinatal deaths in the group with AFI < 5 cm, 3 had a reactive NST within 7 days of fetal death. It is concluded that pregnancy outcome is often poor in the presence of very low AFI and in these cases a reactive NST loses its usual reassuring value. It is suggested that AFI estimation should be included as an integral part of antepartum fetal surveillance of high risk pregnancies.

Vibroacoustic Stimulation - Does it Really Help?

One of the major objectives of perinatal medicine is to look for better means of testing for fetal well-being in utero. This prospectively study measured the antenatal fetal heart rate changes in response to fetal acoustic stimulation using artificial electronic larynx (Model 5C) in two groups of patients. In Group A, consisting of 80 low risk patients selected from the antenatal clinic, the acoustic stimulation resulted in a good response with no perinatal death. In Group B, consisting of 80 high risk patients, only 15 patients (18.7%) showed no response. In these 15 patients, there were two stillbirths and two neonatal deaths. Thirteen of these 15 patients were small for gestational age compared to only eight out of 61 who showed good response to the stimulus. This difference and the findins are statistically significant.

507 Fetal Acoustic Stimulation to Reposition the Fetus in Difficult External Cephalic Versions

507 Fetal Acoustic Stimulation to Reposition the Fetus in Difficult External Cephalic Versions

No evidence of hearing loss due to fetal acoustic stimulation test : Arulkumaran S.; Skurr B.; Tong H.; Kek L.P.; Yeoh K.H.; Ratnam S.S.OBSTET. GYNECOL. (1991) 78/2 (283–285)

The fetal acoustic stimulation test is used increasingly for fetal assessment. To evaluate the possibility of acoustic trauma, 465 children who had been exposed to vibroacoustic stimulation in utero were screened at 4 years of age for high-frequency hearing loss. A hand-held audiometer with test tones at 25 dB for 1000 and 4000 Hz was used because responses at this level indicate hearing within normal limits for middle and high frequencies. Thirty-one children failed the test. Failure to respond was followed by inspection of the ear canal for wax, tympanometry, and reflex measurement to assess the tympanic membrane, middle ear, and eustachian tube. Hearing was retested across the full frequency range using conventional audiometric technique, and referral for otolaryngologic examination and treatment was made if necessary. The causes of hearing loss were impacted wax in 12, current or recent upper respiratory tract infection with eustachian tube dysfunction and middle ear effusion in 15, and unresolved middle ear effusion after treatment with antibiotics for otitis media in two. Profound bilateral sensorineural hearing loss of unknown origin was found in one and slight bilateral gently sloping hearing loss in another. Retesting of all children with conductive hearing loss indicated that hearing had returned to normal after treatment. None of the children showed evidence of hearing loss.

Prenatal Sonographic Diagnosis, Assessment, and Management of a Fetus with a Quadruple Nuchal Cord at 39 Weeks' Gestation

A case of prenatal sonographic diagnosis of a quadruple nuchal cord is presented. Perinatal assessment included nonstress, oxytocin challenge testing, and Doppler velocimetry studies of the umbilical artery and fetal vibratory acoustic stimulation. Obstetric management of this case is discussed.

Sonographic Verification of a Nuchal Cord Following a Vibratory Acoustic Stimulation-Induced Severe Variable Fetal Heart Rate Deceleration with Expedient Abdominal Delivery

A case is presented in which external vibratory acoustic stimulation performed following a nonreactive nonstress test produced a severe variable deceleration of the fetal heart rate. A clinically suspected nuchal cord was confirmed by ultrasound. This rapid precise antepartum diagnosis of cord compression prevented untimely delay and led to immediate abdominal delivery of a nonacidotic, yet hypoxic, infant. This report suggests care be taken when fetal vibratory acoustic stimulation is applied in cases of oligohydramnios and a known existing nuchal cord.

The significance of amniotic fluid volume during intrapartum fetal acoustic stimulation

The relationship of intrapartum fluid volume to the fetal response to acoustic stimulation was investigated in 112 patients who were in the latent phase of labor. Amniotic fluid volume appears to play an insignificant role in the genesis of fetal heart rate decelerations that occur after fetal acoustic stimulation, regardless of the amount of amniotic fluid present.

407 The effect of rupture of fetal membranes (ROM) on fetal acoustic stimulation (FAS) in labor

407 The effect of rupture of fetal membranes (ROM) on fetal acoustic stimulation (FAS) in labor

441 The short term effects of fetal acoustic stimulation (FAS) on fetal swallowing (FS) and amniotic fluid index (AFI)

441 The short term effects of fetal acoustic stimulation (FAS) on fetal swallowing (FS) and amniotic fluid index (AFI)

654 Evaluation of the startle response with antepartum fetal acoustic stimulation

654 Evaluation of the startle response with antepartum fetal acoustic stimulation

Intrauterine Sound Levels: Intrapartum Assessment with an Intrauterine Microphone

The complex mechanisms responsible for fetal hearing are in place and functional by 26 weeks of gestation, but little is known about the acoustic milieu of the amniotic cavity. We placed an electrically isolated microphone in the uterus of nine term gravid volunteers after amniorrhexis. Baseline levels of intrauterine sound were 72 to 88 db. Transabdominal vibroacoustic stimulation with an artificial larynx produced peak mixed frequency sound levels of 91 to 111 db. We conclude that the term fetus in labor is exposed to physiologic sound levels higher than we had anticipated; the application of a quantifiable sound stimulus to the maternal abdominal wall results in a small increment in intrauterine sound; and within the limits specified, experimental fetal acoustic stimulation should pose no major risks.

Fetal acoustic stimulation in the early intrapartum period as a predictor of subsequent fetal condition

Fetal acoustic stimulation has recently received much attention in the literature. This study evaluates fetal acoustic stimulation in the early intrapartum period as a predictor of subsequent fetal condition. The study group consisted of 201 patients, approximately 60% of whom had complicated pregnancies. All were in the latent phase of labor with singleton, vertex-presenting fetuses. Gestational age ranged from 37 to 43 weeks. Fourteen of the 201 fetuses (7%) showed a nonreactive response to fetal acoustic stimulation and those fetuses were at significantly greater risk of initial and subsequent abnormal fetal heart rate patterns, meconium staining, and cesarean delivery because of fetal distress and Apgar scores <7 at both 1 and 5 minutes. Transient fetal heart rate decelerations after a reactive response occurred in 25% of patients; however, fetal outcome was not worse in this group. A reactive response to fetal acoustic stimulation was associated with high specificity and negative predictive values. Therefore we conclude that fetal acoustic stimulation in the early intraprtum period may discriminate the compromised from the noncompromised fetus.

Acoustic Stimulation: Effect on Heart Rate and Other Biophysical Variables

It is clear that external vibroacoustic stimulation produces remarkable changes in fetal heart rate and fetal movement patterns which are related to changes in fetal behavior. The clinical significance of these effects on human fetuses has been addressed by many authors in series of small number of patients involved. There is an obvious lack of uniformity in the different protocols used to determine the predictive value of fetal acoustic stimulation in the assessment of fetal health. Current knowledge of the normal responses of healthy human fetuses to acoustic stimulation and the limitations of this type of testing should be taken into account to determine more accurately the negative and positive predictive value for fetal outcome.

Fetal acoustic stimulation in early labor in patients screened with the admission test

Fetal heart rate reactions to the fetal acoustic stimulation test were investigated in 952 women in early labor. All had cephalic presentations (>33 weeks of gestation) and were screened with a 15-minute fetal heart rate recording (admission test) before the sound stimulation was applied. Three different types of responses were observed: type I, an accelerative response; type II, a biphasic response with acceleration(s) followed by a deceleration; type III, no response or a prolonged deceleration (>60 beats/min and >60 seconds). A type I response was recorded in 98.0% of the women after a reactive admission test result, in 90.2% after an equivocal admission test result, and in 42.9% after an ominous admission test result. Fetal distress in labor occurred in these three groups in 2.0%, 22.2%, and 35.7% of cases, respectively. The risk for fetal distress was high after an ominous admission test and a type III response on the fetal acoustic stimulation test (75.0%). The fetal acoustic stimulation test might be of value in labor and give additional information about fetal well-being in patients previously screened by the admission test. Testing time can be shortened after an equivocal admission test.

Intrapartum assessment of fetal well-being: A comparison of fetal acoustic stimulation with acid-base determinations

Many authorities advocate the use of fetal blood sampling as the final arbiter of abnormal intrapartum fetal heart rate patterns. Alternatively, the presence of an acceleratory fetal heart rate response to scalp stimulation during fetal scalp blood sampling led to the observation that, if present, the likelihood of acidosis was remote. Consequently a prospective intrapartum analysis of evoked accelerations and fetal acid-base status was undertaken. Patients who, on the basis of abnormal fetal heart rate patterns, were judged candidates for acid-base assessment underwent transabdominal acoustic stimulation. The presence or absence of an acceleration was then determined. Sixty-four patients with abnormal intrapartum fetal heart rate patterns underwent intrapartum acoustic stimulation. Thirty fetuses were reactive and all had a pH of greater than or equal to 7.25. Of the 34 fetuses who were nonreactive, 18 were acidotic. This preliminary observation suggests that acoustic stimulation may be a reasonable clinical alternative to fetal blood sampling when a reactive pattern is observed. In the nonreactive fetuses additional evaluation would appear warranted.

Fetal acoustic stimulation testing

Abstract Antepartum fetal heart rate testing, specifically the nonstress test, is of accepted value in the antenatal surveillance of high-risk pregnancies. Fetal rest-activity cycles coupled with arbitrary test intervals appear to lead to falsely nonreactive tests. Methods to alter fetal behavioral states have not been uniformly successful. A retrospective analysis of the adjunctive use of acoustic stimulation at our institution demonstrated a 50% reduction in the number of nonreactive tests. Consequently a prospective randomized clinical trial was undertaken to compare the standard nonstress test with the fetal acoustic stimulation test. Those patients randomized to the fetal acoustic stimulation test underwent transabdominal acoustic stimulation with a Model 5C electronic artificial larynx. The incidence of nonreactive tests was 14% in the control group and 9% in the study group ( K 2 = 11.09, p=0.004). A significant reduction in testing time was also observed. The fetal acoustic stimulation test offers advantages over the traditional nonstress test by lowering the incidence of nonreactive tests and reducing testing time.

Fetal acoustic stimulation testing: II. A randomized clinical comparison with the nonstress test

Antepartum fetal heart rate testing, specifically the nonstress test, is of accepted value in the antenatal surveillance of high-risk pregnancies. Fetal rest-activity cycles coupled with arbitrary test intervals appear to lead to falsely nonreactive tests. Methods to alter fetal behavioral states have not been uniformly successful. A retrospective analysis of the adjunctive use of acoustic stimulation at our institution demonstrated a 50% reduction in the number of nonreactive tests. Consequently a prospective randomized clinical trial was undertaken to compare the standard nonstress test with the fetal acoustic stimulation test. Those patients randomized to the fetal acoustic stimulation test underwent transabdominal acoustic stimulation with a Model 5C electronic artificial larynx. The incidence of nonreactive tests was 14% in the control group and 9% in the study group (K2 = 11.09, p = 0.004). A significant reduction in testing time was also observed. The fetal acoustic stimulation test offers advantages over the traditional nonstress test by lowering the incidence of nonreactive tests and reducing testing time.

Fetal acoustic stimulation testing: A retrospective experience with the fetal acoustic stimulation test

The nonstress test is of accepted value in the surveillance of high-risk pregnancies. In order to improve the efficiency of testing, the authors retrospectively evaluated the adjunctive use of acoustic stimulation testing (FAS-TEST) in 1241 patients who underwent 3464 antepartum fetal heart rate tests. The results were compared to those in the previous 6 months during which time 1307 patients underwent 3573 nonstress tosts. The frequency of nonreactive tests was 12.6% in the nonstress test group and 6.1% in those patients who underwent the FAS-TEST. The antepartum fetal death rates were not significantly different when the two groups were compared. The FAS-TEST decreases the percentage of nonreactive tests in a high-risk population and, as a consequence, may reduce the testing time.