- Email: [email protected]
The effect of vibroacoustic stimulation on the nonstress test at gestational ages of thirty-two weeks or less
Gagnon, Hunse, and Foreman
2. Gagnon R, Hunse C, Carmichael L, et al. External vibratory acoustic stimulation near term: fetal heart rate and heart rate variability responses. AM J OBSTET GYNECOL 1987;156:323-7. 3. Gagnon R, Hunse C, Carmichael L, et al. Human fetal responses to vibratory acoustic stimulation from twenty-six weeks to term. AM] OBSTET GYNECOL 1987;157: 1375-81. 4. Gagnon R, Foreman], Hunse C, Patrick]. Effects oflowfrequency vibration on human term fetuses. AM] OBSTET GYNECOL 1989;161:1479-85. 5. Gagnon R, Patrick], ForemanJ, West R. Stimulation of human fetuses with sound and vibration. AM ] OBSTET GYNECOL 1986;155:848-51. 6. Dawes GS, Redman CWG, Smith ]H. Improvements in the registration and analysis of fetal heart rate records at the bedside. Br J Obstet GynaecoI1985;92:317-25. 7. Patrick], Natale R, Richardson B. Patterns of human fetal breathing activity at 34 to 35 weeks' gestational age. AM ] OBSTET GYNECOL 1978;132:507-13. 8. Bots RSGM, Nijhuis ]G, Martin CB ]r, Prechtl HFR. Human fetal eye movements: detection in utero by ultrasonography. Early Hum Dev 1981;5:87-94. 9. Hicks CR. Fundamental concepts in the design of experiments. 2nd ed. New York: Holt, Rinehart and Winston, 1973:100.
December 1989 Am J Obstet Gyncwl
10. Prechtl HFR, Akiyama Y, Zinkin P, Kerr Grant D. Polygraphic and qualitative analysis. In: Box MCO, Mackeith RC, eds. Studies in infancy. London: Heinemann, 1968: 125. II. Prechtl HFR. The behavioral states of the newborn infant (a review). Brain Res 1974;76:185-212. 12. Brown R, Patrick]. The nonstress test: how long is enough. AM J OBSTET GYNECOL 1981; 141 :646-51. 13. Hutt S], Lenard HG, Prechtl HFR. Psychophysiological studies in newborn infants. Adv Child Dev Behav 1969;4:127-55. 14. Patrick], Campbell K, Carmichael L, et al. Patterns of gross fetal body movements over 24-hour observation intervals during the last 10 weeks of pregnancy. AM] OBSTET GYNECOL 1982;142:363-71. 15. Smith CV, PhelanJP, Platt LD, et al. Fetal acoustic stimulation testing. II. A randomized clinical comparison with the nons tress test. AM] OBSTET GYNECOL 1986;155:131-4. 16. Gerhardt K], Abrams RM, Kovaz BM, et al. Intrauterine noise levels produced in pregnant ewes by sound applied to the abdomen. AM] OBSTET GYNECOL 1988;159:22833.
The effect of vibroacoustic stimulation on the nonstress test at gestational ages of thirty-two weeks or less Maurice L. Druzin, MD, Terri G. Edersheim, MD, J. M. Hutson, MD, and Annette L. Bond, MD New York, New York The effect of vibroacoustic stimulation on the nonstress test at gestational ages of :,;32 weeks was studied in 15 patients who underwent a total of 316 nonstress tests starting at 20 to 25 weeks' gestation. There were 168 nonreactive nonstress tests that were followed by 3 seconds of vibroacoustic stimulation. The incidence of reactive nonstress tests after vibroacoustic stimulation was significantly increased after 26 weeks' gestation. This may have clinical applicability and may be related to functional maturation of the fetal auditory system. (AM J OaslET GVNECOL 1989;161 :1476-8.)
Key words: Vibroacoustic stimulation, nonstress test, pre term delivery Fetal heart rate (FHR) accelerations have long been known to reflect fetal well-being. Vibratory acoustic stimulation has been used over the years to elicit FHR accelerations in an attempt to decrease the falseabnormal (nonreactive) nonstress test. l . 2 Studies have shown that FHR accelerations in response to sound may reflect fetal well-being." 4 This increase in heart rate
From the Department of Obstetrics and Gynecology, The New York Hospital-Cornell Medical Center. Presented in part at the Thzrty-szxth Annual Meeting of the Sonety For Gynecologic Investigation, San Diego, California, March 15-
18, 1989.
Reprmt requests: Maurice L. Druzm, MD, 525 East 68th St., New York, NY 10021. 6/6116239
1476
may be related to a change in fetal state. This has recently been described as a startle response of the fetuS. 5 . 6 Fetal scalp stimulation resulting in FHR acceleration has been correlated with normal acid-base status.' Recently, FHR accelerations in response to vibratory acoustic stimulation have been shown to be predictive of fetal pH in labor. 8 A recent study evaluated fetal accelerations in response to vibratory acoustic stimulation from 26 weeks to term and demonstrated what may be the normal neurodevelopmental status of the fetus. 9 It has been shown that the response to vibratory acoustic stimulation is active as early as 24 weeks' gestation when studied serially from 12 to 32 weeks. 'o This study was undertaken to determine the effect
Vibroacoustic stimulation and nonstress test
Volume 161 l\umber 6. Part 1
1477
Table I. Results of nonstress tests followed by vibratory acoustic stimulation E~tlmated
gestational age (wk)
20-22 22-24 24-26 26-28 28-30 30-32 32-34 34-36 >36 TOTAL
Total NSTs
Nonreactive NST
ReactIVe NST after VAS
16 21 26 30 38 37 34 38 76 316
15 (94%) 18 (86%) 23 (88%) 19(63%) 18 (47%) 18 (49%) 23 (68%)) 14 (37%) 20 (26%) 168
1 (7%) 3 (17%) 5 (22%) 17 (89%) 17 (94%) 18 (100%) 22 (96%) 14 (100%) 19 (95%) 116
NST, Nonstress test; VAS. vibratory acoustic stimulation. The incidence of reactive nonstress tests after vibratory acoustic stimulation was significantly increased after 26 weeks' gestation (p < 0.001).
of vibratory acoustic stimulation on the fetus in terms of the nonstress test at gestational ages from 20 to 32 weeks. Material and methods
Fifteen patients underwent 316 nonstress tests starting at 20 to 25 weeks of gestation. Six patients were volunteers with no obstetric risk factors. Nine patients underwent tests for preterm labor (n = 4), diabetes (n = 2), preeclampsia (n = 1), incompetent cervix (n = 1), or third-trimester bleeding (n = I). The nonstress test is performed with an external system to monitor fetal movement, uterine contractions, and FHR. Uterine activity and fetal movements are obtained with a tokodynamometer strapped to the abdomen in conjunction with manual palpation of the uterus by the examiner. This method will register the frequency and relative duration but not the actual strength of the contractions. The patient is given an "event marker," with which she can register perceived fetal movements on the strip chart. Thus both the patient and the examiner may record fetal movements. The FHR can be derived from ultrasonographic phonocardiogram, or abdominal wall electrocardiogram signals. Ultrasonography will provide an adequate FHR tracing in up to 95% of the cases, while the success rate of the other two methods has been reported as 40% to 60% of cases. A nonstress test is considered reactive (normal) if there are two accelerations of the FHR, ?: 15 beats I min above the baseline, lasting at least 15 seconds, associated with fetal movement in a 20-minute period. A nonstress test is considered nonreactive (abnormal) if the above criteria are (1) not met within an initial 20minute period and (2) not met after vibratory acoustic stimulation is performed in a consecutive 20-minute period. Vibratory acoustic stimulation was performed by us-
ing a single 3-second vibratory acoustic stimulus over the fetal vertex with the use of a Western Electric model 5C electronic artificial larynx. Sound pressure levels of this device measured at 1 m in air averaged 82 dB. Spectral analysis of the artificial larynx shows a fundamental frequency of 80 Hz; harmonics ranging from 20 to 9000 Hz are also observed. The fetal vertex was identified by Leopold maneuvers. In instances where the fetal position was unclear, ultrasonography was used to verify the location of the fetal vertex: FHR response was then observed after vibratory acoustic stimulation and the classification of the nonstress test was then determined. Results
There were 168 nonreactive nonstress tests that were followed by vibratory acoustic stimulation applied for 3 seconds. The incidence of reactive nons tress tests after vibratory acoustic stimulation was significantly increased after 26 weeks of gestation (Table I). All neonates were appropriate for gestational age (>2800 gm) and all had 5-minute Apgar scores >8. One neonatal death was due to neonatal group B (3-hemolytic streptococcal sepsis. There were no congenital anomalies. Comment
A variety of sound frequencies and levels have been used in fetal vibratory acoustic stimulation to obtain a FHR response. It is thought that lower frequencies may evoke fetal tactile vibrational responses, as well as auditory responses. It is also thought that high frequencies (above 1500 Hz) have minimal vibratory influence and that a response is probably auditory in origin." The study of two anencephalic fetuses revealed that there was no fetal response to vibratory acoustic stimulation in the anencephalic fetuses. 12 These authors therefore concluded that the fetal response to vibratory acoustic stimulation is mediated by auditory mecha-
1478 Druzln at
at
nisms. This position is supported by other investigators. 1O Our study supports the impression that fetal response to vibratory acoustic stimulation occurs significantly more frequently after 26 weeks' gestation than before that gestational age. Recent studies suggest that there may be a threshold response to vibroacoustic stimulation. '3 Further studies are warranted to confirm this at various gestational ages. This finding may have clinical applicability and may be related to functional maturation of the fetal auditory system. We acknowledge Audrey Waltner for her assistance. REFERENCES 1. Smith CV, PhelanJP, Paul RH, Broussard P. Fetal acoustic stimulation testing: a retrospective experience with the fetal acoustic stimulation test. AM ] 08STET GYNECOL 1985; 153:567-8. 2. Smith CV. Phelan JP, Platt LD, Broussard P, Paul RH. Fetal acoustic stimulation testing. II. A randomized clinical comparison with the nonstress test. AM] 08STET GyNECOL 1986;155:131-4. 3. Read JA, Miller FC. Fetal heart rate accleration in response to acoustic stimulation as a measure of fetal wellbeing. AM] 08STET GYNECOL 1977;129:512-7. 4. Goodlin RC, Schmidt W. Human fetal arousal levels as
December 1989 Am J Obstet Gynetal
5.
6.
7.
8.
9.
10. 11. 12. 13.
indicated by heart rate recordings. AMJ 085TET GYNECOL 1972; 114:613-21. Divon MY, Platt LD, Cantrell CJ, Smith CV, Yeh SoY, Paul RH. Evoked fetal startle response: a possible intrauterine neurological examination. AMJ 08S1'ET GYNECOL 1985; 153:454-6. Gagnon R, Hunse C, Carmichael L, Fellows F, Patrick J. Effects of vibratory acoustic stimulation on human fetal breathing and gross fetal body movements near term. AM J 08S1'ET GYNECOL 1986;155:1227-30. Clark SL, Gimovsky ML, Miller FC. The scalp stimulation test: a clinical alternative to fetal scalp blood sampling. AM] 08STE1' GYNECOL 1984;148:274-7. Edersheim TG, Hutson]M, Druzin ML, Kogut EA. Fetal heart rate response to vibratory acoustic stimulation predicts fetal pH in labor. AM J 0851'ET GYNECOL 1987; 157: 1557-60. Gagnon R, Hunse C, Carmichael L, Fellows F, Patrick J. Human fetal responses to vibratory acoustic stimulation from twenty-six weeks to term. AM ] 08STET GYNECOL 1987; 157: 1375-81. Birnholz JC, Benacerraf BR. The development of human fetal hearing. Science 1983;222:516-8. Woods JR, Plessinger MA, Barden TP. Stimulating the fetus with sound. Contemp Ob Gyn 1984;23:213-26. Ohel G, Simon A, Linder N, Mor-Yosef S. Anencephaly and the nature of fetal response to vibroacoustic stimulation. Am] Perinatol 1986;3:345-6. Kisilevsky B, Muir DW, Low]A. Human fetal responses to sound as a function of stimulus intensity. Obstet Gynecol 1989;73:971-6.
2. Gagnon R, Hunse C, Carmichael L, et al. External vibratory acoustic stimulation near term: fetal heart rate and heart rate variability responses. AM J OBSTET GYNECOL 1987;156:323-7. 3. Gagnon R, Hunse C, Carmichael L, et al. Human fetal responses to vibratory acoustic stimulation from twenty-six weeks to term. AM] OBSTET GYNECOL 1987;157: 1375-81. 4. Gagnon R, Foreman], Hunse C, Patrick]. Effects oflowfrequency vibration on human term fetuses. AM] OBSTET GYNECOL 1989;161:1479-85. 5. Gagnon R, Patrick], ForemanJ, West R. Stimulation of human fetuses with sound and vibration. AM ] OBSTET GYNECOL 1986;155:848-51. 6. Dawes GS, Redman CWG, Smith ]H. Improvements in the registration and analysis of fetal heart rate records at the bedside. Br J Obstet GynaecoI1985;92:317-25. 7. Patrick], Natale R, Richardson B. Patterns of human fetal breathing activity at 34 to 35 weeks' gestational age. AM ] OBSTET GYNECOL 1978;132:507-13. 8. Bots RSGM, Nijhuis ]G, Martin CB ]r, Prechtl HFR. Human fetal eye movements: detection in utero by ultrasonography. Early Hum Dev 1981;5:87-94. 9. Hicks CR. Fundamental concepts in the design of experiments. 2nd ed. New York: Holt, Rinehart and Winston, 1973:100.
December 1989 Am J Obstet Gyncwl
10. Prechtl HFR, Akiyama Y, Zinkin P, Kerr Grant D. Polygraphic and qualitative analysis. In: Box MCO, Mackeith RC, eds. Studies in infancy. London: Heinemann, 1968: 125. II. Prechtl HFR. The behavioral states of the newborn infant (a review). Brain Res 1974;76:185-212. 12. Brown R, Patrick]. The nonstress test: how long is enough. AM J OBSTET GYNECOL 1981; 141 :646-51. 13. Hutt S], Lenard HG, Prechtl HFR. Psychophysiological studies in newborn infants. Adv Child Dev Behav 1969;4:127-55. 14. Patrick], Campbell K, Carmichael L, et al. Patterns of gross fetal body movements over 24-hour observation intervals during the last 10 weeks of pregnancy. AM] OBSTET GYNECOL 1982;142:363-71. 15. Smith CV, PhelanJP, Platt LD, et al. Fetal acoustic stimulation testing. II. A randomized clinical comparison with the nons tress test. AM] OBSTET GYNECOL 1986;155:131-4. 16. Gerhardt K], Abrams RM, Kovaz BM, et al. Intrauterine noise levels produced in pregnant ewes by sound applied to the abdomen. AM] OBSTET GYNECOL 1988;159:22833.
The effect of vibroacoustic stimulation on the nonstress test at gestational ages of thirty-two weeks or less Maurice L. Druzin, MD, Terri G. Edersheim, MD, J. M. Hutson, MD, and Annette L. Bond, MD New York, New York The effect of vibroacoustic stimulation on the nonstress test at gestational ages of :,;32 weeks was studied in 15 patients who underwent a total of 316 nonstress tests starting at 20 to 25 weeks' gestation. There were 168 nonreactive nonstress tests that were followed by 3 seconds of vibroacoustic stimulation. The incidence of reactive nonstress tests after vibroacoustic stimulation was significantly increased after 26 weeks' gestation. This may have clinical applicability and may be related to functional maturation of the fetal auditory system. (AM J OaslET GVNECOL 1989;161 :1476-8.)
Key words: Vibroacoustic stimulation, nonstress test, pre term delivery Fetal heart rate (FHR) accelerations have long been known to reflect fetal well-being. Vibratory acoustic stimulation has been used over the years to elicit FHR accelerations in an attempt to decrease the falseabnormal (nonreactive) nonstress test. l . 2 Studies have shown that FHR accelerations in response to sound may reflect fetal well-being." 4 This increase in heart rate
From the Department of Obstetrics and Gynecology, The New York Hospital-Cornell Medical Center. Presented in part at the Thzrty-szxth Annual Meeting of the Sonety For Gynecologic Investigation, San Diego, California, March 15-
18, 1989.
Reprmt requests: Maurice L. Druzm, MD, 525 East 68th St., New York, NY 10021. 6/6116239
1476
may be related to a change in fetal state. This has recently been described as a startle response of the fetuS. 5 . 6 Fetal scalp stimulation resulting in FHR acceleration has been correlated with normal acid-base status.' Recently, FHR accelerations in response to vibratory acoustic stimulation have been shown to be predictive of fetal pH in labor. 8 A recent study evaluated fetal accelerations in response to vibratory acoustic stimulation from 26 weeks to term and demonstrated what may be the normal neurodevelopmental status of the fetus. 9 It has been shown that the response to vibratory acoustic stimulation is active as early as 24 weeks' gestation when studied serially from 12 to 32 weeks. 'o This study was undertaken to determine the effect
Vibroacoustic stimulation and nonstress test
Volume 161 l\umber 6. Part 1
1477
Table I. Results of nonstress tests followed by vibratory acoustic stimulation E~tlmated
gestational age (wk)
20-22 22-24 24-26 26-28 28-30 30-32 32-34 34-36 >36 TOTAL
Total NSTs
Nonreactive NST
ReactIVe NST after VAS
16 21 26 30 38 37 34 38 76 316
15 (94%) 18 (86%) 23 (88%) 19(63%) 18 (47%) 18 (49%) 23 (68%)) 14 (37%) 20 (26%) 168
1 (7%) 3 (17%) 5 (22%) 17 (89%) 17 (94%) 18 (100%) 22 (96%) 14 (100%) 19 (95%) 116
NST, Nonstress test; VAS. vibratory acoustic stimulation. The incidence of reactive nonstress tests after vibratory acoustic stimulation was significantly increased after 26 weeks' gestation (p < 0.001).
of vibratory acoustic stimulation on the fetus in terms of the nonstress test at gestational ages from 20 to 32 weeks. Material and methods
Fifteen patients underwent 316 nonstress tests starting at 20 to 25 weeks of gestation. Six patients were volunteers with no obstetric risk factors. Nine patients underwent tests for preterm labor (n = 4), diabetes (n = 2), preeclampsia (n = 1), incompetent cervix (n = 1), or third-trimester bleeding (n = I). The nonstress test is performed with an external system to monitor fetal movement, uterine contractions, and FHR. Uterine activity and fetal movements are obtained with a tokodynamometer strapped to the abdomen in conjunction with manual palpation of the uterus by the examiner. This method will register the frequency and relative duration but not the actual strength of the contractions. The patient is given an "event marker," with which she can register perceived fetal movements on the strip chart. Thus both the patient and the examiner may record fetal movements. The FHR can be derived from ultrasonographic phonocardiogram, or abdominal wall electrocardiogram signals. Ultrasonography will provide an adequate FHR tracing in up to 95% of the cases, while the success rate of the other two methods has been reported as 40% to 60% of cases. A nonstress test is considered reactive (normal) if there are two accelerations of the FHR, ?: 15 beats I min above the baseline, lasting at least 15 seconds, associated with fetal movement in a 20-minute period. A nonstress test is considered nonreactive (abnormal) if the above criteria are (1) not met within an initial 20minute period and (2) not met after vibratory acoustic stimulation is performed in a consecutive 20-minute period. Vibratory acoustic stimulation was performed by us-
ing a single 3-second vibratory acoustic stimulus over the fetal vertex with the use of a Western Electric model 5C electronic artificial larynx. Sound pressure levels of this device measured at 1 m in air averaged 82 dB. Spectral analysis of the artificial larynx shows a fundamental frequency of 80 Hz; harmonics ranging from 20 to 9000 Hz are also observed. The fetal vertex was identified by Leopold maneuvers. In instances where the fetal position was unclear, ultrasonography was used to verify the location of the fetal vertex: FHR response was then observed after vibratory acoustic stimulation and the classification of the nonstress test was then determined. Results
There were 168 nonreactive nonstress tests that were followed by vibratory acoustic stimulation applied for 3 seconds. The incidence of reactive nons tress tests after vibratory acoustic stimulation was significantly increased after 26 weeks of gestation (Table I). All neonates were appropriate for gestational age (>2800 gm) and all had 5-minute Apgar scores >8. One neonatal death was due to neonatal group B (3-hemolytic streptococcal sepsis. There were no congenital anomalies. Comment
A variety of sound frequencies and levels have been used in fetal vibratory acoustic stimulation to obtain a FHR response. It is thought that lower frequencies may evoke fetal tactile vibrational responses, as well as auditory responses. It is also thought that high frequencies (above 1500 Hz) have minimal vibratory influence and that a response is probably auditory in origin." The study of two anencephalic fetuses revealed that there was no fetal response to vibratory acoustic stimulation in the anencephalic fetuses. 12 These authors therefore concluded that the fetal response to vibratory acoustic stimulation is mediated by auditory mecha-
1478 Druzln at
at
nisms. This position is supported by other investigators. 1O Our study supports the impression that fetal response to vibratory acoustic stimulation occurs significantly more frequently after 26 weeks' gestation than before that gestational age. Recent studies suggest that there may be a threshold response to vibroacoustic stimulation. '3 Further studies are warranted to confirm this at various gestational ages. This finding may have clinical applicability and may be related to functional maturation of the fetal auditory system. We acknowledge Audrey Waltner for her assistance. REFERENCES 1. Smith CV, PhelanJP, Paul RH, Broussard P. Fetal acoustic stimulation testing: a retrospective experience with the fetal acoustic stimulation test. AM ] 08STET GYNECOL 1985; 153:567-8. 2. Smith CV. Phelan JP, Platt LD, Broussard P, Paul RH. Fetal acoustic stimulation testing. II. A randomized clinical comparison with the nonstress test. AM] 08STET GyNECOL 1986;155:131-4. 3. Read JA, Miller FC. Fetal heart rate accleration in response to acoustic stimulation as a measure of fetal wellbeing. AM] 08STET GYNECOL 1977;129:512-7. 4. Goodlin RC, Schmidt W. Human fetal arousal levels as
December 1989 Am J Obstet Gynetal
5.
6.
7.
8.
9.
10. 11. 12. 13.
indicated by heart rate recordings. AMJ 085TET GYNECOL 1972; 114:613-21. Divon MY, Platt LD, Cantrell CJ, Smith CV, Yeh SoY, Paul RH. Evoked fetal startle response: a possible intrauterine neurological examination. AMJ 08S1'ET GYNECOL 1985; 153:454-6. Gagnon R, Hunse C, Carmichael L, Fellows F, Patrick J. Effects of vibratory acoustic stimulation on human fetal breathing and gross fetal body movements near term. AM J 08S1'ET GYNECOL 1986;155:1227-30. Clark SL, Gimovsky ML, Miller FC. The scalp stimulation test: a clinical alternative to fetal scalp blood sampling. AM] 08STE1' GYNECOL 1984;148:274-7. Edersheim TG, Hutson]M, Druzin ML, Kogut EA. Fetal heart rate response to vibratory acoustic stimulation predicts fetal pH in labor. AM J 0851'ET GYNECOL 1987; 157: 1557-60. Gagnon R, Hunse C, Carmichael L, Fellows F, Patrick J. Human fetal responses to vibratory acoustic stimulation from twenty-six weeks to term. AM ] 08STET GYNECOL 1987; 157: 1375-81. Birnholz JC, Benacerraf BR. The development of human fetal hearing. Science 1983;222:516-8. Woods JR, Plessinger MA, Barden TP. Stimulating the fetus with sound. Contemp Ob Gyn 1984;23:213-26. Ohel G, Simon A, Linder N, Mor-Yosef S. Anencephaly and the nature of fetal response to vibroacoustic stimulation. Am] Perinatol 1986;3:345-6. Kisilevsky B, Muir DW, Low]A. Human fetal responses to sound as a function of stimulus intensity. Obstet Gynecol 1989;73:971-6.