Fetal acoustic stimulation, an adjunct to external cephalic version: A blinded, randomized crossover study

GENERAL OBSTETRICS AND GYNECOLOGY Fetus-Placenta-Newborn Fetal acoustic stimulation, an adjunct to external cephalic version: A blinded, randomized crossover study Robert L. Johnson, MD, and John P. Elliott, MD Phoenix, Arizona OBJECTIVE: Our purpose was to determine whether fetal acoustic stimulation can improve the chance of successful external cephalic version in patients at 36 to 38 weeks' gestation with fetal midline spine position. STUDY DESIGN: A randomized, blinded crossover trial was performed. In this "N of 1" study, the patient served as her own control. RESULTS; Twenty-six patients were enrolled in the study, and three were excluded due to engagement of the fetal breech. In the initial trial with fetal acoustic stimulation to the maternal abdomen, 12 of 12 (100%) changed position to spine lateral and 11 of 12 (92%) were successfully verted. In the control group (fetal acoustic stimulation to nurse's arm), none of 11 (0%) changed position to spine lateral and one of 11 (9%) were successfully verted (p < 0.0001). In the crossover trial eight of 10 (80%) of the original placebo (control) patients were successfully verted after fetal acoustic stimulation to the maternal abdomen and none of 1 (0%) from the original treatment group were successfully verted after placebo fetal acoustic stimulation (p < 0.0001). Combined data from the original and crossover trials indicates 19 of 22 (86%) successful versions after fetal acoustic stimulation to maternal abdomen compared with one of 12 (8%) that had successful external cephalic version after placebo fetal acoustic stimulation. CONCLUSION: Fetal acoustic stimulation shifts fetal position to spine lateral, which increases successful version of fetuses with midline fetal spine presentations. (AM J OBSTETGYNECOL1995;173:1369-72.)

Key words" Fetal acoustic stimulation, external cephalic version, fetal position

Fetal acoustic stimulation has recently been recognized as a technique for repositioning the fetus for varying obstetric procedures. Fetal acoustic stimulation elicits a "startle response" that promotes fetal movement and fetal heart rate changes. Sarno and Bruner ~ used fetal acoustic stimulation to reposition the fetus for diagnostic uhrasonography with reported satisfactory results in 94.1% of their study patients. Nyman et al. ~ reported 90% maternal perception of fetal movement with fetal acoustic stimulation. Fetal acoustic stimulation has also been used successfully to enhance antepartum fetal heart rate monitoring? Nonreactive nonstress tests were decreased from 13.8% to 6.8% in the fetal acoustic stimulation group. Habituation to sound stimulation may indicate additional reassurance of fetal well-being, as shown in a study by Smith et al. 4 From the Phoenix Perinatal Associates, Good Samaritan Regional Medical Center. Received for publication January 17, 1995; revised January' 30, 1995; accepted February 21, 1995. Reprint ~quests: Robert L. Johnson, MD, Phoenix Perinatal Associates, 1450 S. Dobson Road, Suite 321B, Mesa, AZ 85202. Copyright © 1995 by Mosby-Year Book, Inc. 0002-9378/95 $5.00 + 0 6/1/64422

Nonhabituation was associated with a higher incidence of cesarean section for fetal distress and placental abnormalities. Strong et al? recently used acoustic stimulation to elicit fetal recoil in labor. All (100%) patients demonstrating fetal recoil had umbilical arterial p H > 7.20 compared with five of nine (55%) without fetal recoil, who had an arterial p H < 7.20 at delivery. External cephalic version is a technique that can reduce the incidence of breech presentation at labor and delivery. Eller and VanDorsten ~ reported that 15% of cesarean deliveries are performed for breech presentation, which adds $1.4 billion to United States obstetric costs. Zhang et al. 7 recently reviewed the literature concerning external cephalic version and concluded that it is successful in approximately 65% of attempts (range 48% to 77%) with almost 100% remaining vertex until labor. The mean cesarean rate after successful external cephalic version was 37% compared with 83% for unsuccessful attempts. They concluded that external cephalic version could reduce the cost associated with breech delivery by 12.3%. Prognostic features associated with reduced success in attempting external cephalic version include maternal 1369

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November 1995 Am .] Obstet Gynecol

Table I. Maternal and fetal characteristics of patients in study

Characteristic I MeanandSD I Range [ No. Maternal age (yr) Parity Gestational age at ECV Infant weight (kg)

25.9 (5.3) 2.4 (1.8) 37.2 (1.1) 3.2 (0.3)

16-35 1-8 36-39.8

23 23 23

2.7-3.9

23

ECV, External cephalic version. obesity, an anterior placenta, oligohydramnios, ruptured amniotic membranes, engagement of the presenting fetal part, low parity, type of breech, and orientation of the fetal spine to the maternal midline. J o h n s o n et al. ~ recently r e p o r t e d preliminary observations on the use of fetal acoustic stimulation to enhance the success of external cephalic version in patients with a midline fetal spine position. T h e fetus was successfully repositioned to a spine lateral position in all patients with 94% successful external cephalic version. We present the outcome of a blinded, randomized crossover trial using fetal acoustic stimulation for repositioning midline fetal spine position.

Material and methods This study was conducted in the antepartum evaluation areas of Good Samaritan Regional Medical Center in Phoenix, Arizona, and Desert Samaritan Hospital in Mesa, Arizona, during a 2-year period, Jan. 1, 1993, to Dec. 31, 1994. Patients scheduled for attempted external cephalic version had an ultrasonographic examination to determine fetal spine position. If the spine was in a midline (either back-up or back-down) position, the patient was offered participation in the study. Informed consent was obtained. Our external cephalic version protocol excludes patients for any of the following reasons: oligohydramnios as defined by an amniotic fluid index < 5 cm, fetal or uterine anomalies, ruptured amniotic membranes, active labor, engagement of presenting part, or fetal heart rate decelerations. Patients were randomized by selecting sequential envelopes that had been generated by a table of r a n d o m numbers. After consent was obtained, the nurse selected a sealed envelope, which revealed the treatment group to which the patient would be assigned. One half would have fetal acoustic stimulation to the fetal a b d o m e n and one half would have the fetal acoustic stimulation applied to the nurse's arm (placebo). A Western Electric Division AT&T (Phoenix) model 5C Electrolarynx was used, and a 1- to 3-second stimulus was applied to maternal a b d o m e n over the fetal head or the u p p e r arm of the nurse. External cephalic version was attempted by attending physicians (nine physicians for 22 patients). The efficacy of fetal acoustic stimulation was assessed by both a change in fetal spine location and the ability to

successfully complete the external cephalic version. T h e physicians returned to the room and performed another ultrasonographic examination to determine any effect on fetal position. External cephalic version was then attempted. If the attempt was successful, the data were recorded and the trial was over. If the attempt was unsuccessful, the physician left the room and the nurse would apply fetal acoustic stimulation again to either the patient's a b d o m e n or to her own arm, whichever was not used in the first trial (crossover). Another ultrasonographic examination was done for position and a second attempt was made at external cephalic version. The physicians were blinded throughout the trial. A number of descriptions have been used for single patient experiments including "N of 1" trials, single patient clinical trials, crossover and self-controlled research designs, and single patient randomized clinical trials. T h e objective o f " N of 1" experiments is to find the best treatment for a particular patient. "N of 1" experiments are useful in answering questions of efficacy of treatment when the physician or the patient doubts that it is present, in studies of rare or unusual disorders that do not lend to large randomized clinical trials, in rapid assessment of Outcomes, and in situations where little or no carryover between treatment periods is present. Four critical components are necessary: randomization (usually crossover), blinding of physician to treatment assignment (reduces operator bias), defining and quantifying outcomes, and explicit criteria for evaluating efficacy of treatment. Prestudy power analysis indicated an "N of 1" sample size of 20, which was exceeded in this study and gives power of 0.9 for an c~level equal to 0.05 for the two hypotheses. T h e ~('~and Fisher's exact statistics were used to analyze the data.

Results Twenty-six patients with midline fetal spine position were identified and randomized into the study. No patient declined to be randomized. Three patients were excluded from the study group after randomization (one treatment, two control). During the initial external cephalic version attempt the breech was discovered to be deeply engaged. None of these fetuses shifted to spine lateral position after fetal acoustic stimulation. All further external cephalic version attempts were discontinued. Demographic characteristics of the 23 patients are shown in Table I. There was no difference in any characteristic between treatment groups. Placental attachment was anterior in seven, fundal in six, lateral in four, and posterior in six. Route of delivery and fetal spine position are shown in Table II. In the treatment group (12 patients), 12 (100%) were successfully converted to the spine lateral position and 11 of 12 (91%) underwent successful version. In the placebo group (11

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Johnson and Elliott 1371

Table II. Comparison of treatment (fetal acoustic stimulation to abdomen) with control (fetal acoustic stimulation to nurse's arm)

Initial trial No. of patients Position change to spine lateral Successful version

Treatmenl I Control I Significance

Crossovertrial Treatment I Control ]Significance

12 12 (100%)

11 0 (0%)

p = 0.0001"

10 10 (100%)

11 (92%)

1 (9%)

p = 0.0001"

8 (80%)

1 1 (100%) 0 (0%)

p = 0.0001t

*By both X~ and Fisher's exact test. tBy Fisher's exact test. patients), none (0%) were successfully converted to the spine lateral position and one (9%) underwent successful version (p < 0.0001). The crossover arm was then analyzed. In the original placebo group 10 patients were eligible for crossover to the treatment group. T e n (100%) of these patients were successfully converted to the spine lateral position and eight (80%) underwent successful version. In the original treatment group one patient was still breech and eligible for crossover to the placebo group. One (100%) of these patients was successfully converted to the spine lateral position and none (0%) underwent successful version (p < 0.0001). Combining both the initial and crossover trials, one of 12 (8%) patients had a successful version after placebo treatment compared with 19 of 22 (86%) successful versions after fetal acoustic stimulation to the maternal abdomen. M1 patients who were successfully vetted remained vertex at the time of labor. Eight patients were eventually delivered by cesarean section (eight of 23, 34.7%); only three were due to persistent breech presentation after external cephalic version failure with fetal acoustic stimulation. The remainder were performed due to other obstetric complications in vertex presentations. One h u n d r e d percent of fetuses undergoing fetal acoustic stimulation changed from midline to lateral spine position. No adverse fetal outcomes related to external cephalic version with fetal acoustic stimulation were noted in this study.

Comment External cephalic version has become an accepted method to decrease cesarean section deliveries for breech presentation. Among the various prognostic factors for external cephalic version outcome, only three (oligohydramnios, fetal engagement, and fetal spine orientation) are amenable to change. This study addresses the issue of alteration of fetal spine orientation with fetal acoustic stimulation, which was shown to be safe and efficacious. In Table III data from the current study are combined with those from our earlier trial? Thirty-nine fetuses were identified with spine midline presenta-

Table III. Combined studies with fetal acoustic stimulation

I No. of patients Position change to lateral Successful version

FAS 38 38 (100%) 34 (90%)

I NoFAS 39 0 (0%) 1 (3%)

FAS, Fetal acoustic stimulation. tions. Thirty-eight fetuses remained breech without fetal acoustic stimulation and a single fetus was successfully verted. With the use of fetal acoustic stimulation, all remaining fetuses shifted to spine lateral positions (100%) and 34 (90%) underwent successful version after fetal acoustic stimulation to the maternal abdomen. During the 2-year study period the institutional total deliveries were 24,096 with 386 (1.6%) attempted external cephalic versions with a 56.2% successful version rate. The combined cesarean section rate in successful versions was 21% (seven of 34), slightly higher than a combined institutional cesarean section rate of 20.1% for the study period. The overall cesarean section rate was 29% (11/39) compared with 97% in the failure group, which compares with the results of Zhang et al., 7 who reported a 37% cesarean section rate in the successful external cephalic version group and 83% in controls. Obstetric use of fetal acoustic stimulation continues to expand. Fetal acoustic stimulation has been used adjunctively to enhance antenatal testing by reducing biophysical profile '~ and nonstress test testing time,'" evaluate fetal well-being during the intrapartum period," and repositioning (fetal shifting) to enhance uhrasonographic imaging and fetal procedures. ~ There have been no reported adverse outcomes with the use of fetal acoustic stimulation. Arulkumaran et al. ':~ screened 465 children after in utero fetal acoustic stimulation and fi)und no evidence of hearing loss at 4 years of age. The logical use of fetal acoustic stimulation to facilitate fetal shifting to a prognostically favorable position (lateral spine orientation associated with higher success rates) for external cephalic version has been demonstrated in this study. Similar outcomes in

Abrams et al,

November 1995 Am J Obstet Gynecol

the preliminary and current study support the use of fetal acoustic stimulation at external cephalic version in patients with midline fetal spine position. This study demonstrates an increase in vaginal deliveries, which would translate into reduced cost. The "N of 1" study design allows meaningful interpretation of data in a small sample size and studies of conditions with low incidence, because the patient becomes her own control. Because blinding of treatment a r m s was accomplished, differences of ef[brt during external cephalic version should not be present. Results of this study would support that fetal acoustic stimulation should be used to facilitate external cephalic version when the fetal breech presents with a midline fetal spine position.

REFERENCES 1. Sarno AP Jr, Bruner JP. Fetal acoustic stimulation as a possible adjunct to diagnostic obstetric ultrasound: a preliminary report. J Obstet Gynecol 1990;76:668-70. 2. Nyman M, Arulkumaran S, Jakobsson J, Westgren M. Vibroacoustic stimulation in high risk pregnancies: materhal perception of fetal movements, fetal heart rate and fetal outcome. J Perinat Med 1992;20:267-74. 3. Tongson T, Piyamongkol W. Comparison of the acoustic

stimulation test with nonstress test: a randomized, controlled clinical trial. J Reprod Med 1994;39:17-20. 4. Smith CV, Davis SR, Rayburn WE Nelson RM. Fetal habituation to vibroacoustic stimulation in uncomplicated term pregnancies. Am J Perinat 1991;8:380-2. 5. Strong TH Jr, Jordan DL, Marden DW. The fetal recoil test. AMJ OBSTETGYNECOL1992;167:1382-3. 6. Eller DE VanDorsten JP. Breech presentation. Curr Opin Obstet Gynecol 1993;5:664-8. 7. Zhang J, Bowes WA Jr, Formey J. Efficacy of external cephalic version: a review. Obstet Gynecol 1993;82:30612. 8. Johnson RL, Strong TH Jr, Radin T, Elliott J. Fetal acoustic stimulation as an adjunct to external cephalic version. J Reprod Med [In press]. 9. Inglis SR, Druzin ML, Wagner WE, Kogut E. The use of vibroacoustic stimulation during the abnormal or equivocal biophysical profile. Obstet Gynecol 1993;82:371-4. 10. Miller-Slade D, Gloeb DJ, Bailey S, et al. Acoustic stimulation-induced fetal response compared to traditional nonstress testing. J Obstet Gynecol Neonatol Nurs 1991; 20:160-7. 11. Sarno AP, Ahn MO, Phelan JP, Paul RH. Fetal acoustic stimulation in the early intrapartum period as a predictor of subsequent fetal condition. AMJ OBSTETGVnECOL1990; 162:762-7. 12. Phelan JP. Acoustic stimulation during third trimester. Contemp OB/GYN 1991;36:87-94. 13. Arulkumaran S, Skurr B, Tong H, Kek LP, Yeoh KH, Ratnam SS. No evidence of hearing loss due to fetal acoustic stimulation test. Obstet Gynecol 1991;78:283-5.

Fetal acoustic stimulation test: Stimulus features of three artificial larynges recorded in sheep Robert M. Abrams, PhD," b Kenneth Aemil J.M. Peters"

j. Gerhardt, PhD, c Cesar Rosa, MD," and

Gainesville, Florida OBJECTIVE: The purpose of the current study was to evaluate the characteristics of vibroacoustic devices used for fetal stimulation. STUDY DESIGN: Intrauterine sound pressure levels over a frequency range of 40 to 5000 Hz were measured with hydrophones in anesthetized sheep. Stimulators included the AT&T (Martinsburg, W.V.) and Servox (Hearing Instruments, Piscataway, N.J.) artificial larynges, the Corometrics fetal acoustic stimulator (Wallingford, Conn.) and an electric toothbrush. RESULTS: Intrauterine spectral patterns resulting from stimulation with the AT&T, Servox, and Corometrics devices were characterized by numerous high-level overtones above a fundamental frequency between 97 and 163 Hz. Fundamental frequencies recorded during toothbrush stimulation were 22 to 24 Hz with reduced but identifiable overtones up to 250 Hz. CONCLUSIONS: Fetal vibroacoustic stimulators that operate on the principle of the electronic artificial larynx produce very similar intrauterine sound pressure levels. (AM J OBSTETGYNECOL1995;173:1372-6.)

Key words: Vibroacoustic stimulation, artificial larynx, sheep From the Departments of Obstetrics and Gynecology," Pediatrics/' and Communication Processes and Disorders,' University of Florida College of Medicine. Supported by National Institutes of Health grant No. HD20084. Received for publication September 15, 1994; revised December 14, 1994; accepted March 7, 1995. 1372

Reprint requests: Robert M, Abrams, PhD, University of Florida College of Medicine, Departments of Obstetrics and Gynecology, P.O. Box 100294, Gainesville, FL 32610-0294. Copyright © 1995 by Mosby-Year Book, Inc. 0002-9378/95 $5.00 + 0 6/1/64629