International Journal of Pediatric Otorhinolaryngology, @ Elsevier/North-Holland Biomedical Press
1 (1979)
221
221-229
THE RISK OF HEARING IMPAIRMENT IN CHILDREN FROM MOTHERS EXPOSED TO NOISE DURING PREGNANCY
Z. SZMEJA,
Z. SLOMKO,
Otolaryngological Medicine, Poznati (Received (Accepted
K. SIKORSKI
Clinic, Obstetrical (Poland)
and H. SOWI~SKI
Clinic and Department
of Physics,
Academy
of
December, 1978) August 30th, 1979)
INTRODUCTION
The inner ear of the foetus from women exposed to noise during pregnancy is affected by acoustic stimuli. Foetal audiometry has revealed that an acoustic stimulus of considerable intensity (about 100 decibels), if applied to the abdominal wall of a pregnant woman, causes a change in heart action, an acceleration of heart rhythm by lo-15 beats/min [7,9,15]. Sontag and Wallace [22] found an acceleration of the heart action due to vibratory stimuli, and Sontag and Richards [23] observed the same due to acoustic stimuli. This effect is greatest at 20-4000 Hz and smallest at 40005000 Hz [ 61. Similar findings were made by Murphy and Smyth [ 171. Bench and Vass [ 51 suggest that the heart acceleration results from the mother’s reaction to acoustic stimuli. On protecting the mothers from acoustic stimuli, by masking the tone through the headphones, no acceleration of foetal heart action was observed. A normal development of cochlea and sensory end-organ has been found in foetus in the 24th week of intrauterine life [2,18]. In 27--2%week prematures, a change in the rhythm of heart action on exposure to acoustic stimulus can be observed [11,13,17]. Electroencephalographic examinations on 32-week prematures revealed potential oscillations, and in 34-week prematures distinct evoked responses caused by acoustic stimuli [ 14,211. Foetal movements following acoustic stimulation are also observed. The first to describe this was Whitehead in 1876 (see ref. 15), and similar observations have been made by Peiper [ 191, Forbes and Forbes [ 123, Sontag and Wallace [ 221 and Fleischer [ 111. The above findings show that acoustic stimuli reaching the inner ear of the foetus are strong enough to excite the foetus and the heart acceleration and movements provide evidence of its discomfort. Stronger acoustic stimuli may even induce morphological changes. Arvy [l], who used very strong acoustic stimuli with rats in their intrauterine
lives, revealed an impairing effect resulting in inborn defects such as cleft palate, underdevelopment of limbs, and others. Daniel [S] using Preyer’s pinna reflex plotted audiometric curves in 100 young guinea pigs exposed throughout their foetal lives to noise in a weaving shop. Hearing acuity determinations were carried out on days 3,7,14, 30 and 60 after birth. In successive determinations progressive hearing impairment was observed, even despite the fact that the acoustic traumatizing factor ceased at the time of birth. Up to the 14th day after birth hearing impairment was found in 50% of guinea pigs and at 60 days signs of hearing impairment due to acoustic trauma were observed in all cases. Laciak et al. [16] drew attention to a risk of hearing impairment in children whose mothers worked in noisy conditions during their pregnancies. Those authors examined 75 children and found perceptive hearing loss of varied degree in 35 (about 50%). In those children all other factors which might have impaired their hearing ability were excluded. In 40-50% of children examined for deafness, Sobieszczanska-Radoszewsko [ 201 could not find the reason for hearing loss. All these doubtful cases cannot, of course, be referred to acoustic trauma during the mother’s pregnancy, but this possibility cannot be excluded. The abdomen and uterus walls work as protection from acoustic trauma for the inner ear of the foetus. The measurements of the damping values of the walls are rather divergent. Bench [ 31 found these values to be as follows: 19 dB at 200 Hz, 24 dB at 500 Hz, and 38 dB at 1000 Hz. In their experiments on animals (goats) Bench et al. [4] observed an increase in the damping values as the pregnancy advanced. The measurements by Walker et al. [26] revealedvalues as follows: 20 dB at 50-100 Hz, 25 dB at 200 Hz, 37 dB at 1000 Hz, and 50 dB at 2000 Hz. In their investigations Klosterkijtter and Mitarbeiter [15] found damping values of 14-40 dB. Etienne et al. [lo] found much lower values - with ultrasounds they obtained 9.4 dB at 2 MHz. The development of industry and the ever-increasing employment of women, especially in the textile industry, as well as exposure to noise from the environment (jet planes and other sources of noise) arouse the fear that all these noisy conditions may affect the foetuses in pregnant women and impair the foetal inner ear. In order to find out if the noise of the environment may exert an impairing effect upon the inner ear of the foetus of the mother working in noisy conditions, some experiments on animals were carried out and measurements of the damping values of the abdomen and uterus wall were taken. ANIMAL
EXPERIMENTS:
MATERIAL
AND METHODS
Ten guinea pigs whose mothers were exposed to noise of 95-100 dB in a factory hall throughout their pregnancy were used. The noise was continual, with a 12 h break once a week. The newborn guinea pigs were moved from noise environment to normal conditions. Every few days Preyer’s reflex was
223
examined with Peters audiometer. Thereafter, the reaction to succinic dehydrogenase activity was carried out in one cochlea under amythal-ether anaesthesia using an operation microscope. On decapitation of the animal, both of its cochleae were excised for further histological preparation. Seven pm sections of one cochlea were stained with haematoxylin and eosin, toluidine blue and PAS, and Brachet reactions were carried out. The same examinations were performed in the controls. The above methods were used since, as known from other authors and our own investigations, a decrease in succinic dehydrogenase activity in hearing cells and some degenerative changes within the Corti organ and spiral ganglion were observed after exposure to acoustic trauma [ 24,251. Preyer ‘s reflex The reflex was observed from the 2nd to the 20th day of life. Its values were the same in both the animals exposed to noise in their foetal lives and in the controls. Histological and histochemical examinations Histological examinations did not reveal any changes characteristic of acoustic trauma within the Corti organ and spiral ganglion. Microscopic pictures in either group of animals were the same. Histochemical examinations of cochlear structures in experimental and control animals did not show any significant differences. The succinic dehydrogenase activities in the hearing cells of the animals of either group were similar. RNA content in the cytoplasm of spiral ganglion cells was the same in the experimental and control i?lhIldS.
MEASUREMENTS
OF DAMPING
VALUES
OF THE ABDOMEN
AND UTERUS
WALLS
The object of these investigations was to determine the value of acoustical isolation of female abdominal integument. The investigations were carried out on 44 normal healthy women. The acoustical isolation value of the integument was calculated by means of the equation: I = L, - L* where I is the acoustical isolation of integument, L1 is the sound intensity on the outer side of integument and Lz is the sound intensity on the inner side of integument. The investigations were carried out with two different methods. (I) In the first method the measuring set-up was as presented in Fig. 1 and included a precision sound level meter (PSLM, type Briiel-Kjaer 2707), an octave filter (T-OF, type BK 1613), a stethoscope tube (ST) as used for obstetric auscultation and a pressure connecting hose (PCH). The first measurements were performed before the child was born. The
224
Fig. 1. Block diagram of measurement arrangements used by the first method.
stethoscope tube (ST) was closely applied to the abdomen of the pregnant woman where the heart action of the foetus was best audible. The sounds of the heart action of the foetus were conveyed through the ST and pressure connecting hose (PCH) to the microphone of the precision sound level meter (PSLM). The use of an octave filter (T-OF) made it possible to determine not only the sound pressure level LZ in the range of 20 Hz-20kHz (the so-called “Lin” measurement) but also that in the first three octaves of middle frequencies 31.5 Hz, 63 Hz and 125 Hz (LZ’, LZ2, Ls3). The second measurement was performed with the same measuring set-up immediately after the child was born, applying the ST to the heart area of the newborn. In this way the sound pressure levels Li, L,’ and L13 were determined. Using the previous equation, the value of acoustical isolation of the abdominal integument of a pregnant woman in the last stage of pregnancy was determined and, subsequently, the arithmetic mean from 14 measurements calculated. The values of the arithmetic mean for “Lin” and first three octaves are presented in Table I and in Fig. 2, interrupted line. (II) In the second method the measuring set-up was as presented in Fig. 3 and included a white noise generator (WNG, type BK 1405), a power amplifier (PA, type BK 2706), loudspeakers (LS1 and LS2), a hydrophone (H, type BK 8103), a preamplifier (P, type BK 2626), an octave filter (T-of-l/3, type BK 1616) and a PSLM (BK 2209). The white noise generator (WNG), power amplifier (PA) and two loudspeakers produced the white noise of constant level of intensity in the room TABLE I The middle frequency (Hz) of octave-filter set type 1613
31.5
Arithmetic mean of isolation (dB) from 14 cases
10.4
63
10.7
125
14.9
lin 20 Hz-20 11.5
kHz
225
32 c 30. 2626w
24.
z!J22g 20_
~
Second
------
Frst
J i -
161614.
z2
12,O_--T--J
*
r--,
I
B642-
I 31.5
63
method method
I : II 1 I I I II I
125
Fig. 2. Sound
isolation
500
of female
1000
1
I
2500
5000
abdominal
I I I I I
1 ’ ’ ; n,
F r eq’:eb,
integument
during last part of pregnancy.
in which the patient was placed. The hydrophone (H) pick-up was inserted through the vagina and cervical canal into the uterine cavity at the posterior wall of the body of the uterus. The hydrophone insertion was preceded by a thorough disinfection of the vulva and perineum and internal examination. The hydrophone and its tube were sterilized at high temperature. The hydrophone thus placed was isolated from the surroundings by the abdominal integument, the anterior wall of the uterus and a layer of amniotic fluid. During the measurements the patient was laid on the bed so that the loudspeakers generating the white noise were on both her sides at the level of the abdominal cavity. During all the measurements the course of labour pains and the heart action of the foetus were recorded by means of a cardiotopograph (KTO). The total time of the measurement did not exceed 5-10 min. All the measurements were made in the presence of an obstetrician and were carried out in the band 20 Hz (“Lin” measurement) and in l/3 octave bands from 400 Hz to 10 kHz.
a PA
BK1405
Fig. 3. Block
BK2706
diagram
of measurement
arrangements
used by the second
method.
226 TABLE II The middle frequency (Hz) of thirdactave filter set type 1616
Arithmetic mean of isolation (dB) from 19 cases
400 500 630 800 1,000 1,250 1,600 2,000 2,500 3,150 4,000 5,000 6,300 8,000 10,000 Lin 20 Hz
10.1 16.4 19.9 18.9 20.6 23.9 21.2 19.0 25.7 27.8 28.7 20.2 11.6 5.6 4.6 12.1
TABLE III The middle frequency (Hz) of third-octave filter set type 1616
Arithmetic mean of isolation (dB) from 11 cases
200 250 315 400 500 630 800 1,000 1,250 1,600 2,000 2,500 3,150 4,000 5,000 6,300 8,000 10,000 12,500 16,000 20,000 Lin 20 Hz-20
2.9 5.9 6.2 8.1 19.3 20.5 23.4 20.5 23.6 25.7 28.2 31.7 31.3 29.9 27.4 26.6 21.5 19.2 20.2 15.3 13.5 12.6
kHz
227
Fig. 4. Sound isolation Second method.
of female
abdominal
integument
during
early
part
of pregnancy.
The second measurement was performed with the same measuring set-up in the absence of the patient. The differences in sound pressure levels measured in the first and second measurements determined the isolation value of the abdominal integument of the women in the frequency range given. The values of the arithmetic mean are shown in Table II and Fig. 2, 4 (continuous line). Making use of the measuring set-up employed in Method II, measurements were made of acoustical isolation of abdominal integument in women in the early stage of pregnancy. The investigations were performed on patients immediately after abortion. The principle of the measurement was exactly the same as that described in Method II. Analyses were made in the band 20 Hz-20 kHz (“Lin”) and in l/3 octave bands (from about 200 Hz to 20,000 kHz). The investigation included 11 individuals. The arithmetic mean values from 11 cases for all the l/3 octave bands and the 20 Hz-20 kHz band (“Lin”) are shown in Fig. 4. Data of sound isolation (dB) of woman’s abdomen integument in early stage of pregnancy are shown in Table III. DISCUSSION
Our results obtained from experiments on guinea pigs were not indicative of an impairing effect of noise on the inner ear of the foetus and did not confirm Daniel’s observations. The damping values of the abdomen and uterus walls from our investigations are lower than those obtained previously [5,15,26]. They are, however, slightly higher than the values obtained by Etienne et al. [lo], which may be accounted for by the application of ultrasounds. The damping values in the early months of pregnancy were some-
228
what greater than just before delivery, which may be due to the thicker wall of the uterus. We could not confirm the observations by Bench et al. [4] that the damping values increase as the pregnancy advances. Our results, as well as those obtained by the authors mentioned above, may indicate that working with a noise intensity not exceeding 90 dB should not be harmful to the inner ear of the foetus. There are moments, however, when the noise suddenly increases and exceeds the norm of 90 dB. The observations on the changes of foetal heart rhythm and movements also give evidence that an acoustic stimulus of about 100 dB causes anxiety and discomfort in the foetus. They also provide evidence that a rather large amount of acoustic energy penetrates into the inner ear of the foetus. We do not know how vulnerable the inner ear of the foetus is to the acoustic trauma; it may be more vulnerable than in adults. The possibility of the acoustic trauma adding its harmful effect to other harmful factors such as ototoxic drugs, maternal diseases, vibration, etc., has also to be taken into account. As is known, under such conditions even stimuli of lesser intensity, which normally would cause no harmful effects, may produce an impairment. Our opinion is that, until the above mentioned problems have been cleared up, it is safer to prevent pregnant women from working in noisy conditions. ACKNOWLEDGEMENT
The electroacoustical measuring equipment was gratuitously put at our disposal by Briiel-Kjaer Company. REFERENCES 1 Arvy, A., Effect of noise during pregnancy upon foetal viability and development. In B. Welch and A. Welch (Eds.), Physiological Effects of Noise, Plenum Press, New York, London, 1970, p. 91. 2 Bast, T. and Anson, B., The Temporal Bone and the Ear, Thomas, Springfield, Ill., 1949. 3 Bench, J., Sound transmission to the human foetus through the maternal abdominal wall, J. gent. Psychol., 113 (1968) 85. 4 Bench, J., Anderson, J. and Hoare, M., Measurement system for foetal audiometry, J. acoust. Sot. Amer., 47 (1970) 1602. 5 Bench, J. and Vass, A., Fetal audiometry, Lancet, 1 (1970) 91. 6 Bernard, J, and Sontag, W., Fetal reactivity to tonal stimulation: a preliminary report, J. genetic Psychol., 70 (1947) 205. 7 Calvet, J., Coil, J., Laredo, G. and Camillieri, L., Les reactions uditives chez le nouvenu-ne et le foetus, Folia phoniatrica, 24 (1972) 427. 8 Daniel, R., Effects of weaving shop noise on the auditory organ of guinea-pig fetuses, Otolaryng. pol., 30 (1976) 337. 9 Dwomicka, B., Jasidska, Smolarz, W. and Wawryk, B., Attempt of determining the foetal reaction to acoustic stimulation, Acta oto-laryng. (Stockh.), 57 (1964) 571. 3!O Etienne, J., Filipczynski, L., Firek, A., Groniowski, J., Kretowicz, J., Lypacewicz, S.
229
11 12 13 14 15
16
17 18 19 20 21 22 23 24
25 26
and Salkowski, J., Pomiary in vivo natezenia zogniskowanej wiazki ultradiwiekowej stosowanej w ultrasonografii wczesnej ciazy, Arch. akustyki, 11 (1976) 35. Fleischer, K., Untersuchungen zur Entwicklung der Innenohrfunktion, Z. Laryng. Rhinol., 34 (1955) 733. Forbes, H.S. and Forbes, H.D., Fetal sense reactions: hearing, J. camp. Psychol., 7 (1927) 353 (according to ref. 15). Johansson, H., Wedenberg, E. and Westin, B., Measurement of tone response by human foetus, Acta oto-laryng. (Stockh.), 57 (1964) 188. Joppich, G. and Schulte, J., Neurologie des Neugeborenen, Springer, 1968. Klosterkotter, W. and Mitarbeiter, Experimentale Untersuchungen zur Frage der Larmgrenzwerte fiir werdende Mutter am Arbeitsplatz. Bundesanstalt fiir Arbeitsschutz und Unfallforschung, Forschungsbericht nr. 132,1974, Dortmund, pp. l-81. Laciak, J. and Majcherska-Matuchniak, B., Zachowanie sie s,luchu u dzieci matek pracujacych w hdasie. Pam. XXVII Zjazdu Otolaryngologow Polskich, Katowice, 1968, PZWL, Warszawa, 1970, p. 155. Murphy, Y. and Smyth, C., Responses of foetus to auditory stimulation, Lancet, 5 (1962) 972. Ormerod, F., The Pathology of Congenital Deafness in the Child. The Modern Educational Treatment of Deafness, 1960. Manchester University Press. Peiper, A., Sinnesempfindungen des Kindes vor seiner Geburt. Mschr. Kinderheilk., 29 (1924) 236. Sobieszczadska-Radoszewska, L., Analysis of causes of hearing damage in children examined in the first year of life, Otolaryng. polska, 27 (1973) 477. Sontag, L. and Newbery, H., Normal variations of the heart rate during pregnancy, Amer. J. Obstet. Gynecol., 40 (1940) 449. Sontag, L. and Wallace, R., Changes in rate of human fetal heart in response to vibratory stimuli, Amer. J. Dis. Child., 51 (1936) 583. Sontag, L. and Richards, T., Studies in fetal behavior: I. Fetal heart rate as a behavioral indicator, Child. Develop. Monogr., 3 (1936) 72. Sowihski, H., Szmeja, Z., Gawronski, Z. and Waciawik, W., Zmiany histologiczne i histochemiczne w uchu wewnetrznym po urazie akustycznym i wpl’yw ochronny witaminy A. Pam. XXVII Zjazdu Otolaryngologow Polskich, Katowice, 1968, PZWL, Warszawa, 1970, p. 151. Szmeja, Z., SowiAski, H. and Bialek, E., The condition of hearing and inner ear in animals exposed to high-intensity noise in foetal life, Otolaryng. pol., 29 (1975) 11. Walker, J., Grimwade, J. and Wood, C., Intrauterine noise: a component of the foetal environment, J. Obstet. Gynecol., 1 (1971) 91.
1 (1979)
221
221-229
THE RISK OF HEARING IMPAIRMENT IN CHILDREN FROM MOTHERS EXPOSED TO NOISE DURING PREGNANCY
Z. SZMEJA,
Z. SLOMKO,
Otolaryngological Medicine, Poznati (Received (Accepted
K. SIKORSKI
Clinic, Obstetrical (Poland)
and H. SOWI~SKI
Clinic and Department
of Physics,
Academy
of
December, 1978) August 30th, 1979)
INTRODUCTION
The inner ear of the foetus from women exposed to noise during pregnancy is affected by acoustic stimuli. Foetal audiometry has revealed that an acoustic stimulus of considerable intensity (about 100 decibels), if applied to the abdominal wall of a pregnant woman, causes a change in heart action, an acceleration of heart rhythm by lo-15 beats/min [7,9,15]. Sontag and Wallace [22] found an acceleration of the heart action due to vibratory stimuli, and Sontag and Richards [23] observed the same due to acoustic stimuli. This effect is greatest at 20-4000 Hz and smallest at 40005000 Hz [ 61. Similar findings were made by Murphy and Smyth [ 171. Bench and Vass [ 51 suggest that the heart acceleration results from the mother’s reaction to acoustic stimuli. On protecting the mothers from acoustic stimuli, by masking the tone through the headphones, no acceleration of foetal heart action was observed. A normal development of cochlea and sensory end-organ has been found in foetus in the 24th week of intrauterine life [2,18]. In 27--2%week prematures, a change in the rhythm of heart action on exposure to acoustic stimulus can be observed [11,13,17]. Electroencephalographic examinations on 32-week prematures revealed potential oscillations, and in 34-week prematures distinct evoked responses caused by acoustic stimuli [ 14,211. Foetal movements following acoustic stimulation are also observed. The first to describe this was Whitehead in 1876 (see ref. 15), and similar observations have been made by Peiper [ 191, Forbes and Forbes [ 123, Sontag and Wallace [ 221 and Fleischer [ 111. The above findings show that acoustic stimuli reaching the inner ear of the foetus are strong enough to excite the foetus and the heart acceleration and movements provide evidence of its discomfort. Stronger acoustic stimuli may even induce morphological changes. Arvy [l], who used very strong acoustic stimuli with rats in their intrauterine
lives, revealed an impairing effect resulting in inborn defects such as cleft palate, underdevelopment of limbs, and others. Daniel [S] using Preyer’s pinna reflex plotted audiometric curves in 100 young guinea pigs exposed throughout their foetal lives to noise in a weaving shop. Hearing acuity determinations were carried out on days 3,7,14, 30 and 60 after birth. In successive determinations progressive hearing impairment was observed, even despite the fact that the acoustic traumatizing factor ceased at the time of birth. Up to the 14th day after birth hearing impairment was found in 50% of guinea pigs and at 60 days signs of hearing impairment due to acoustic trauma were observed in all cases. Laciak et al. [16] drew attention to a risk of hearing impairment in children whose mothers worked in noisy conditions during their pregnancies. Those authors examined 75 children and found perceptive hearing loss of varied degree in 35 (about 50%). In those children all other factors which might have impaired their hearing ability were excluded. In 40-50% of children examined for deafness, Sobieszczanska-Radoszewsko [ 201 could not find the reason for hearing loss. All these doubtful cases cannot, of course, be referred to acoustic trauma during the mother’s pregnancy, but this possibility cannot be excluded. The abdomen and uterus walls work as protection from acoustic trauma for the inner ear of the foetus. The measurements of the damping values of the walls are rather divergent. Bench [ 31 found these values to be as follows: 19 dB at 200 Hz, 24 dB at 500 Hz, and 38 dB at 1000 Hz. In their experiments on animals (goats) Bench et al. [4] observed an increase in the damping values as the pregnancy advanced. The measurements by Walker et al. [26] revealedvalues as follows: 20 dB at 50-100 Hz, 25 dB at 200 Hz, 37 dB at 1000 Hz, and 50 dB at 2000 Hz. In their investigations Klosterkijtter and Mitarbeiter [15] found damping values of 14-40 dB. Etienne et al. [lo] found much lower values - with ultrasounds they obtained 9.4 dB at 2 MHz. The development of industry and the ever-increasing employment of women, especially in the textile industry, as well as exposure to noise from the environment (jet planes and other sources of noise) arouse the fear that all these noisy conditions may affect the foetuses in pregnant women and impair the foetal inner ear. In order to find out if the noise of the environment may exert an impairing effect upon the inner ear of the foetus of the mother working in noisy conditions, some experiments on animals were carried out and measurements of the damping values of the abdomen and uterus wall were taken. ANIMAL
EXPERIMENTS:
MATERIAL
AND METHODS
Ten guinea pigs whose mothers were exposed to noise of 95-100 dB in a factory hall throughout their pregnancy were used. The noise was continual, with a 12 h break once a week. The newborn guinea pigs were moved from noise environment to normal conditions. Every few days Preyer’s reflex was
223
examined with Peters audiometer. Thereafter, the reaction to succinic dehydrogenase activity was carried out in one cochlea under amythal-ether anaesthesia using an operation microscope. On decapitation of the animal, both of its cochleae were excised for further histological preparation. Seven pm sections of one cochlea were stained with haematoxylin and eosin, toluidine blue and PAS, and Brachet reactions were carried out. The same examinations were performed in the controls. The above methods were used since, as known from other authors and our own investigations, a decrease in succinic dehydrogenase activity in hearing cells and some degenerative changes within the Corti organ and spiral ganglion were observed after exposure to acoustic trauma [ 24,251. Preyer ‘s reflex The reflex was observed from the 2nd to the 20th day of life. Its values were the same in both the animals exposed to noise in their foetal lives and in the controls. Histological and histochemical examinations Histological examinations did not reveal any changes characteristic of acoustic trauma within the Corti organ and spiral ganglion. Microscopic pictures in either group of animals were the same. Histochemical examinations of cochlear structures in experimental and control animals did not show any significant differences. The succinic dehydrogenase activities in the hearing cells of the animals of either group were similar. RNA content in the cytoplasm of spiral ganglion cells was the same in the experimental and control i?lhIldS.
MEASUREMENTS
OF DAMPING
VALUES
OF THE ABDOMEN
AND UTERUS
WALLS
The object of these investigations was to determine the value of acoustical isolation of female abdominal integument. The investigations were carried out on 44 normal healthy women. The acoustical isolation value of the integument was calculated by means of the equation: I = L, - L* where I is the acoustical isolation of integument, L1 is the sound intensity on the outer side of integument and Lz is the sound intensity on the inner side of integument. The investigations were carried out with two different methods. (I) In the first method the measuring set-up was as presented in Fig. 1 and included a precision sound level meter (PSLM, type Briiel-Kjaer 2707), an octave filter (T-OF, type BK 1613), a stethoscope tube (ST) as used for obstetric auscultation and a pressure connecting hose (PCH). The first measurements were performed before the child was born. The
224
Fig. 1. Block diagram of measurement arrangements used by the first method.
stethoscope tube (ST) was closely applied to the abdomen of the pregnant woman where the heart action of the foetus was best audible. The sounds of the heart action of the foetus were conveyed through the ST and pressure connecting hose (PCH) to the microphone of the precision sound level meter (PSLM). The use of an octave filter (T-OF) made it possible to determine not only the sound pressure level LZ in the range of 20 Hz-20kHz (the so-called “Lin” measurement) but also that in the first three octaves of middle frequencies 31.5 Hz, 63 Hz and 125 Hz (LZ’, LZ2, Ls3). The second measurement was performed with the same measuring set-up immediately after the child was born, applying the ST to the heart area of the newborn. In this way the sound pressure levels Li, L,’ and L13 were determined. Using the previous equation, the value of acoustical isolation of the abdominal integument of a pregnant woman in the last stage of pregnancy was determined and, subsequently, the arithmetic mean from 14 measurements calculated. The values of the arithmetic mean for “Lin” and first three octaves are presented in Table I and in Fig. 2, interrupted line. (II) In the second method the measuring set-up was as presented in Fig. 3 and included a white noise generator (WNG, type BK 1405), a power amplifier (PA, type BK 2706), loudspeakers (LS1 and LS2), a hydrophone (H, type BK 8103), a preamplifier (P, type BK 2626), an octave filter (T-of-l/3, type BK 1616) and a PSLM (BK 2209). The white noise generator (WNG), power amplifier (PA) and two loudspeakers produced the white noise of constant level of intensity in the room TABLE I The middle frequency (Hz) of octave-filter set type 1613
31.5
Arithmetic mean of isolation (dB) from 14 cases
10.4
63
10.7
125
14.9
lin 20 Hz-20 11.5
kHz
225
32 c 30. 2626w
24.
z!J22g 20_
~
Second
------
Frst
J i -
161614.
z2
12,O_--T--J
*
r--,
I
B642-
I 31.5
63
method method
I : II 1 I I I II I
125
Fig. 2. Sound
isolation
500
of female
1000
1
I
2500
5000
abdominal
I I I I I
1 ’ ’ ; n,
F r eq’:eb,
integument
during last part of pregnancy.
in which the patient was placed. The hydrophone (H) pick-up was inserted through the vagina and cervical canal into the uterine cavity at the posterior wall of the body of the uterus. The hydrophone insertion was preceded by a thorough disinfection of the vulva and perineum and internal examination. The hydrophone and its tube were sterilized at high temperature. The hydrophone thus placed was isolated from the surroundings by the abdominal integument, the anterior wall of the uterus and a layer of amniotic fluid. During the measurements the patient was laid on the bed so that the loudspeakers generating the white noise were on both her sides at the level of the abdominal cavity. During all the measurements the course of labour pains and the heart action of the foetus were recorded by means of a cardiotopograph (KTO). The total time of the measurement did not exceed 5-10 min. All the measurements were made in the presence of an obstetrician and were carried out in the band 20 Hz (“Lin” measurement) and in l/3 octave bands from 400 Hz to 10 kHz.
a PA
BK1405
Fig. 3. Block
BK2706
diagram
of measurement
arrangements
used by the second
method.
226 TABLE II The middle frequency (Hz) of thirdactave filter set type 1616
Arithmetic mean of isolation (dB) from 19 cases
400 500 630 800 1,000 1,250 1,600 2,000 2,500 3,150 4,000 5,000 6,300 8,000 10,000 Lin 20 Hz
10.1 16.4 19.9 18.9 20.6 23.9 21.2 19.0 25.7 27.8 28.7 20.2 11.6 5.6 4.6 12.1
TABLE III The middle frequency (Hz) of third-octave filter set type 1616
Arithmetic mean of isolation (dB) from 11 cases
200 250 315 400 500 630 800 1,000 1,250 1,600 2,000 2,500 3,150 4,000 5,000 6,300 8,000 10,000 12,500 16,000 20,000 Lin 20 Hz-20
2.9 5.9 6.2 8.1 19.3 20.5 23.4 20.5 23.6 25.7 28.2 31.7 31.3 29.9 27.4 26.6 21.5 19.2 20.2 15.3 13.5 12.6
kHz
227
Fig. 4. Sound isolation Second method.
of female
abdominal
integument
during
early
part
of pregnancy.
The second measurement was performed with the same measuring set-up in the absence of the patient. The differences in sound pressure levels measured in the first and second measurements determined the isolation value of the abdominal integument of the women in the frequency range given. The values of the arithmetic mean are shown in Table II and Fig. 2, 4 (continuous line). Making use of the measuring set-up employed in Method II, measurements were made of acoustical isolation of abdominal integument in women in the early stage of pregnancy. The investigations were performed on patients immediately after abortion. The principle of the measurement was exactly the same as that described in Method II. Analyses were made in the band 20 Hz-20 kHz (“Lin”) and in l/3 octave bands (from about 200 Hz to 20,000 kHz). The investigation included 11 individuals. The arithmetic mean values from 11 cases for all the l/3 octave bands and the 20 Hz-20 kHz band (“Lin”) are shown in Fig. 4. Data of sound isolation (dB) of woman’s abdomen integument in early stage of pregnancy are shown in Table III. DISCUSSION
Our results obtained from experiments on guinea pigs were not indicative of an impairing effect of noise on the inner ear of the foetus and did not confirm Daniel’s observations. The damping values of the abdomen and uterus walls from our investigations are lower than those obtained previously [5,15,26]. They are, however, slightly higher than the values obtained by Etienne et al. [lo], which may be accounted for by the application of ultrasounds. The damping values in the early months of pregnancy were some-
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what greater than just before delivery, which may be due to the thicker wall of the uterus. We could not confirm the observations by Bench et al. [4] that the damping values increase as the pregnancy advances. Our results, as well as those obtained by the authors mentioned above, may indicate that working with a noise intensity not exceeding 90 dB should not be harmful to the inner ear of the foetus. There are moments, however, when the noise suddenly increases and exceeds the norm of 90 dB. The observations on the changes of foetal heart rhythm and movements also give evidence that an acoustic stimulus of about 100 dB causes anxiety and discomfort in the foetus. They also provide evidence that a rather large amount of acoustic energy penetrates into the inner ear of the foetus. We do not know how vulnerable the inner ear of the foetus is to the acoustic trauma; it may be more vulnerable than in adults. The possibility of the acoustic trauma adding its harmful effect to other harmful factors such as ototoxic drugs, maternal diseases, vibration, etc., has also to be taken into account. As is known, under such conditions even stimuli of lesser intensity, which normally would cause no harmful effects, may produce an impairment. Our opinion is that, until the above mentioned problems have been cleared up, it is safer to prevent pregnant women from working in noisy conditions. ACKNOWLEDGEMENT
The electroacoustical measuring equipment was gratuitously put at our disposal by Briiel-Kjaer Company. REFERENCES 1 Arvy, A., Effect of noise during pregnancy upon foetal viability and development. In B. Welch and A. Welch (Eds.), Physiological Effects of Noise, Plenum Press, New York, London, 1970, p. 91. 2 Bast, T. and Anson, B., The Temporal Bone and the Ear, Thomas, Springfield, Ill., 1949. 3 Bench, J., Sound transmission to the human foetus through the maternal abdominal wall, J. gent. Psychol., 113 (1968) 85. 4 Bench, J., Anderson, J. and Hoare, M., Measurement system for foetal audiometry, J. acoust. Sot. Amer., 47 (1970) 1602. 5 Bench, J. and Vass, A., Fetal audiometry, Lancet, 1 (1970) 91. 6 Bernard, J, and Sontag, W., Fetal reactivity to tonal stimulation: a preliminary report, J. genetic Psychol., 70 (1947) 205. 7 Calvet, J., Coil, J., Laredo, G. and Camillieri, L., Les reactions uditives chez le nouvenu-ne et le foetus, Folia phoniatrica, 24 (1972) 427. 8 Daniel, R., Effects of weaving shop noise on the auditory organ of guinea-pig fetuses, Otolaryng. pol., 30 (1976) 337. 9 Dwomicka, B., Jasidska, Smolarz, W. and Wawryk, B., Attempt of determining the foetal reaction to acoustic stimulation, Acta oto-laryng. (Stockh.), 57 (1964) 571. 3!O Etienne, J., Filipczynski, L., Firek, A., Groniowski, J., Kretowicz, J., Lypacewicz, S.
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