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Data on the significance of fetal arrhythmia
Data on the significance of fetal arrhythmia. B. KOMAROMY, M.D. ]. GAAL, M.D. G. MIHALY, M.D. P. MOCSARY, M.D. 6. POHANKA, M.D. S. SURANYI, M.D. Debrecen, Hungary
Fetal arrhythrnia as an indication, of fetal distress is judged rather diversely in atticles in the obstetric literature. In 5 patients in whom premature beat and arrhythmia were observed, we made a continuous recording of FHR and fetal acid-base balance. Such cornplex exarninations in our opinion provide the earliest and ;nost trustworthy
indication of fetal distress. Nevertheless, we found fetal acidosis in none of our cases. Such arrhythmias do not necessitate intervention because, in themselves, they are not dependable signs of fetal distress.
A c c o R o r N G to classical obstetric teaching fetal heart arrhythmia is one sign of fetal distress. Although this view has been generally accepted, occasional contradictory reports have appeared in the literature. Redman 1 established that certain types of fetal arrhythmia are of good prognosis and do not require intervention. The value of his investigations is limited by the fact that he analyzed fetal heart function by auscultation and made ECG recordings only of the newborn. Much more convincing are the data of Hon and Huang 2 who analyzed fetal arrhythmia using the electrocardiogram. In his cases although arrhythmia was detected during labor and delivery, infants of perfect general condition were born, and it was assumed that arrhythmia resulted from increased vagus tonus and not hypoxia. In our opinion the earliest possible recognition of fetal distress is facilitated by continuous complex investigations, and during delivery we have shown a correlation of ECG recordings of fetal heart function with
the fetal acid-base balance. 3 In this report we wish to present data regarding the significance of fetal arrhythmia. Methods and materials
During delivery fetal heart function was recorded continuously by ECG with abdominal or vaginal electrodes. Our method was described in our previous communication. 4 ' 5 The fetal phonocardiogram was recorded simultatteously. The pH value of the fetal scalp blood was determined during labor by the method of Saling. 6 The color of the amniotic fluid and its pH value were determined continuously throughout labor in the manner already described. 3 After delivery the pH vaiue of the biood from the umbilical cord was determined before the newborn infant took its first breath. The Apgar scoring was used to estimate the condition of the newborn and in every case ECG recordings of the newborn were made both directly after delivery and during the days following. Fetal heart function was recorded using an 8 channel Polyregistrator ( Officine Galileo, Florence), and pH determinations were carried out using As-
From the University Department of Obstetrics and Gynecology.
79
Komaromy et al.
80
Am.
September I, 1967 J. Obst. & Gynec.
Table I. Fetal arrhythmia, pH values of amniotic fluid, and fetal blood (data on newborn infants in our cases)
I
I
A Arrhythmia
Cases
ILength
Form
.. mnwllc
of time Color
fl Ul'd
I Actual
I values* pH
1.
Premature beats, Two days dur- Clear arrhythmia ing pregnancy, then after loading 15 minutes
2.
Premature beats
3.
Supraventricuiar 2 hours, 30 Ciear premature minutes durbeats ing delivery
7.05 7.11
4.
Ventricular pre- 5 hours, 20 Clear mature beats, minutes durquadrigeminal ing delivery pulse
5.
Supraventricular 7 hours, 20 Clear premature minutes durbeats, bigeming delivery iny, trigeminy, arrhythmia
Actual pH values of urnbilical blood
pH values of scalp blood*
Vein
I
Artery
I
Newborn
Apgar score
I
EGG
8
Normal
7.38
7.30
10
Normal
7.26 7.33
7. 34
7.28
10
Normal
6.90 7.04
7.23 7.29
7.31
7.26
9
6.98 7.10
7.24 7.30
7.34
7.25
10
2 hours during Clear delivery
Ventricular premature beats lasts 24 hours Premature beats of several foci, sinoauricular block lasts 21 days
*Of the serial measurements, the first number is the lowest obtained, the second shows the average value .
~sec
I ES
I ES
I :
~
I
ES
\ ES
I
I
:
I
ES
I
ES
I
I
rr'~~~~,_-J~~f"~,.-"~~~t' Fig. 1. Fetal premature beat. Simultaneously recorded fetal phonocardiogram (upper tracing) and electrocardiogram (lower tracing). ES, ventricular premature beat.
trup Micro Equipment (Radiometer, Copenhagen). During our investigations, we found 5 cases of fetal arrhythmia. On one occasion using the loading test recommended by Ron and Wohlgemuth/ we observed fetal premature beats and arrhythmia. In a further 4 cases, rhythmic disturbances developed during delivery and persisted until the end of the delivery.
Results
The results of our investigations are summarized in Table I. Two of the more interesting cases will be described in detail. Case reports Case 1. Mrs. M. Gy., aged (Case 4, Table I) . This was and the patient was admitted because of premature rupture
35, is a multipara a term pregnancy to our d epartment of the membranes.
Volume 99 Number 1
Significance of fetal arrhythmia
81
Fig. 2. Fetal quadrigeminy. Simultaneously recorded fetal phonocardiogram (upper tracing) and electrocardiogram (lower tracing). ES, ventricular premature beat.
M
M
Fig. 3. Fetal bigeminy. Synchronously recorded fetal electrocardiogram from the maternal abdominal wall (upper tracing) and phonocardiogram (lower tracing). F, fetal; M, maternal complexes.
The fetal heart sounds were rhythmical with a frequency of 130 per minute. Uterine contractions started spontaneously 8 hours after the rupture of the membranes, whereupon fetal arrhythmia appeared, and, therefore, continuous observations were made of fetal heart function and acid-base balance during the remainder of labor. From the picture obtained using a vaginal electrode (Fig. 1) it can be seen that the rhythm was disturbed by premature ventricular beats; the extra complexes were split, broadened, and biphased. Clear amniotic fluid was voided through a catheter introduced into the amnion cavity and its pH value together with
that of the scalp blood was within normal physiologic values. Continuous observations '.vere made for a further 5 hours, 20 minutes, until the end of the delivery. Heart function remained arrhythmic during the later stages of labor but the irregular premature beats were replaced here and there by quadrigeminal pulse (Fig. 2). During this stage of labor, the pH values of the amniotic fluid and scalp blood were within normal physiologic limits. The mother was not given drugs during labor. The newborn infant weighed 3,500 grams and had an Apgar score of 9. The pH values of the blood from the umbilical artery and vein were normal. Premature
82
Septcmb<·t 1, J'H;·;
Kom6romy et al.
'\m . .J . Oh!'t .
~ < ;~· n r·t
t
M
M , J
~'\...I1 ,I
I
y
ES Fig. 4. Fetal trigeminy. Synchronously recorded fetal electrocardiog ram from the maternal abdominal wall ( upper tracing ) and phonocardiogram (low er tracing ) . F. fet al: M. matl"rnal complexes; ES, supraventricular premature bear.
1 sec
Fig. 5. Fetal arrhythmia and premature beat. Synchronously recorded fetal electrocardiogram (upper tracing) and phonocardiogram (lower tracing). ES, supraventricular premature beat.
ventricular beats were detected only occasionally in the newborn. Forty-eight hours after delivery the heart function was normal with no cardiac murmur and the condition of the newborn was faultless. Case 2. Mrs. B. N. Gy., aged 21, is a multipara (Case 5, Table I ). This was a term pregnancy and the patient was transferred to our
clinic from the Maternity Home when fetal arrhythmia was detected during the first stage of parturition. Continuous complex recordings were begun immediately. The ECG record from the maternal abdominal wall revealed irregularly occuring premature supraventricular beats alternating with bigeminy ( Fig. 3) and trigeminy (Fig. 4 ). The form of thP extra complex did not
Significance of fetal arrhythmia
Volume 99 Number I
83
Fig. 6. Fetal bradycardia and premature beat. Synchronously recorded fetal electrocardiogram (upper tracing) and phonocardiogram (lower tracing ) . ES, interpolated premature beat.
~
I
~...... H.. .- ..... . ~
Fig. 7. Fetal arrhythmia. Synchronously recorded fetal electrocardiogram (upper tracing ) and phonocardiogram (lower tracing) .
differ from the others. The amniotic fluid was clear and its pH value as well as that of the scalp blood was normal. Obsetvations were continued for 7 hours, 20 minutes, until the end of the delivery. Arrhythmia increased during labor. In the vaginally recorded ECG arrhythmia, compensated premature supraventricular beats could be observed (Fig. 5) . After it interpolated premature beats appeared in deep bradycardia ( 70 per minute ) (Fig. 6) and immediately before delivery a very serious arrhythmia devel-
oped (Fig. 7). Despite all this the ammottc fluid remained clear and its pH value together with that of the scalp blood was normal. The patient was not given drugs during labor. The newborn infant weighed 3,050 grams and was in good general condition (Apgar score 10 ). The pH values of blood taken from the umbilical cord was within the normal limits. The ECG of the newborn infant revealed premature beats of several foci and a sinoauricular block which remained in an alternating form for 21 days after
84
~t'ph·mlw:
Kom6romy et ol. \tiL
delivery. During this period, the general condition of the infant was faultl<'ss and a detaih'd pediatric examination found no heart disease. At the age of 4 months the infant's heart function was regular.
Comment
Salingn recommended examination of capillary blood from the scalp to determine fetal intrauterine acidosis. The actual pH value of the blood is the resultant of the factors maintaining acid-base balance. From a clinical viewpoint, its determination in itself affords suitable information about the momentary condition of the fetus and is much more reliable than the measuring of the p0 2 •8 Though Rooth, Sjostedt, and Caligara, 9 and Schreiner1 " have shown that the pH value of the amniotic fluid also provides information on gaseous exchange in the fetus (in certain cases we ourselves have found it so3 ) so far this problem has not been settled.n In our investigations of fetal heart function and gaseous exchange we were able to show that in the cases we examined arrhythmia was not correlated with acidosis. This was further borne out by measurement of the pH value of the umbilical cord blood immediately after delivery and the good general condition of the newborn. Hon~ has suggested that in arrhythmia characterized by irregularly occurring premature beats the disorder of the exciting and conducting system of the heart is due to an increased vagus tonus. In the cases we examined) the amniotic fluid did not contain meconium and the mnbilical cord was not twisted around the shoulders or neckthese being conditions in which the role of the vagus would be markedly emphasized. According to Unghvary, 1 " multiple foci
f
()h..,t,
l, 19~·i7 & (;~II("'~
premature beat~, or bi--. tri·, and yuadn~em mal pulse in adults are frequently of myocardial origln: but we have been unable to find any report dealing with similar permanent fetal arrhythmia in the literature. Freistadt 1 " reported a case of transient fetal bigeminy, but the newborn had no heart disease. In Case 5 (Table Il we first thought that the arrhythmia might be due to a cono-enital disorder of the excitation and con" ducting system of the heart, but we were unable to demonstrate cardiac disease in the newborn. Our data support the view that arrhythmia caused by premature beats is more frequent during delivery than during pregnancy. It appears to be a transient functional disorder (increased vagus tonus?) which generally disappears after delivery. However, one report 14 in the literature suggests that premature heartbeats may be caused by congenital malformation of the heart. Our own results suggest that such arrhythmia, whether due to an increased vagus tonus or a heart defect, does. n~t require intervention as this arrhythmia m itself is not a sign of fetal distress. In our present study the interdependence of fetal heart rate and acid-base balance was investigated in a special field. The detailed analysis of this interdependence in different clinical situations comprises the further objectives for study. We hereby express our gratitude to Dr. E. H. Hon, Yale University, N'ew Haven, Connecticut, for placing the vaginal electrode wnstructed by him at our disposal, and to our colleague Dr. T. Kaszas, University Department of Pediatrics, Debrecen, for his very gerwrous help in thl' checkup of the newborn.
REFERENCES
1. Redman, T. F.: J. Obst. & Gynaec. Brit. Emp. 65: 304, 1958.
2. Ron, E. H., and Huang, H. S.: Obst. & Gynec. 20: 81, 1962. . 3. Suranyi, s., Gaal, J., Komaromy B., M!ltaly, Gy., Mocsary, P., and Pohanka, 0.: Lancet 1: 744, 1966,
4. Komliromy, B., Gaal, J., Mihaly_, Gy., Mocsary, P., Pohanka, 0., an
Volume 99 Number I
7. Hon, E. H., and Wohlgemuth, R.: AM. J. 0BST. & GYNEG. 81; 361, 1961. 8. Saling, E.; Das Kind im Bereich der Geburtshilfe, Stuttgart, 1966, Georg Thieme Verlag. 9. Rooth, G., Sjostedt, S., and Caligara, F.: AM. J. 0BST. & GYNEC. 81: 4, 1961. 10. Schreiner, W. F.: Fruchtwasser und Fetus, Basel/New York, 1964, S. Karger, AG.
Significance of fetal arrhythmia
85
11. Rooth, G., and Sjovall, A.: Lancet 2: 371, 1966. 12. Unghvary, L.: KHnikai es kiserleti elektrokardiographia, Budapest 1958, Medicina. 13. Freistadt, H.: AM.]. 0BST. & GYNEC. 84: 13, 1962. 14. Dippel, A. L.: AM. J. OssT. & GYNEC. 27: 120, 1934.
Fetal arrhythrnia as an indication, of fetal distress is judged rather diversely in atticles in the obstetric literature. In 5 patients in whom premature beat and arrhythmia were observed, we made a continuous recording of FHR and fetal acid-base balance. Such cornplex exarninations in our opinion provide the earliest and ;nost trustworthy
indication of fetal distress. Nevertheless, we found fetal acidosis in none of our cases. Such arrhythmias do not necessitate intervention because, in themselves, they are not dependable signs of fetal distress.
A c c o R o r N G to classical obstetric teaching fetal heart arrhythmia is one sign of fetal distress. Although this view has been generally accepted, occasional contradictory reports have appeared in the literature. Redman 1 established that certain types of fetal arrhythmia are of good prognosis and do not require intervention. The value of his investigations is limited by the fact that he analyzed fetal heart function by auscultation and made ECG recordings only of the newborn. Much more convincing are the data of Hon and Huang 2 who analyzed fetal arrhythmia using the electrocardiogram. In his cases although arrhythmia was detected during labor and delivery, infants of perfect general condition were born, and it was assumed that arrhythmia resulted from increased vagus tonus and not hypoxia. In our opinion the earliest possible recognition of fetal distress is facilitated by continuous complex investigations, and during delivery we have shown a correlation of ECG recordings of fetal heart function with
the fetal acid-base balance. 3 In this report we wish to present data regarding the significance of fetal arrhythmia. Methods and materials
During delivery fetal heart function was recorded continuously by ECG with abdominal or vaginal electrodes. Our method was described in our previous communication. 4 ' 5 The fetal phonocardiogram was recorded simultatteously. The pH value of the fetal scalp blood was determined during labor by the method of Saling. 6 The color of the amniotic fluid and its pH value were determined continuously throughout labor in the manner already described. 3 After delivery the pH vaiue of the biood from the umbilical cord was determined before the newborn infant took its first breath. The Apgar scoring was used to estimate the condition of the newborn and in every case ECG recordings of the newborn were made both directly after delivery and during the days following. Fetal heart function was recorded using an 8 channel Polyregistrator ( Officine Galileo, Florence), and pH determinations were carried out using As-
From the University Department of Obstetrics and Gynecology.
79
Komaromy et al.
80
Am.
September I, 1967 J. Obst. & Gynec.
Table I. Fetal arrhythmia, pH values of amniotic fluid, and fetal blood (data on newborn infants in our cases)
I
I
A Arrhythmia
Cases
ILength
Form
.. mnwllc
of time Color
fl Ul'd
I Actual
I values* pH
1.
Premature beats, Two days dur- Clear arrhythmia ing pregnancy, then after loading 15 minutes
2.
Premature beats
3.
Supraventricuiar 2 hours, 30 Ciear premature minutes durbeats ing delivery
7.05 7.11
4.
Ventricular pre- 5 hours, 20 Clear mature beats, minutes durquadrigeminal ing delivery pulse
5.
Supraventricular 7 hours, 20 Clear premature minutes durbeats, bigeming delivery iny, trigeminy, arrhythmia
Actual pH values of urnbilical blood
pH values of scalp blood*
Vein
I
Artery
I
Newborn
Apgar score
I
EGG
8
Normal
7.38
7.30
10
Normal
7.26 7.33
7. 34
7.28
10
Normal
6.90 7.04
7.23 7.29
7.31
7.26
9
6.98 7.10
7.24 7.30
7.34
7.25
10
2 hours during Clear delivery
Ventricular premature beats lasts 24 hours Premature beats of several foci, sinoauricular block lasts 21 days
*Of the serial measurements, the first number is the lowest obtained, the second shows the average value .
~sec
I ES
I ES
I :
~
I
ES
\ ES
I
I
:
I
ES
I
ES
I
I
rr'~~~~,_-J~~f"~,.-"~~~t' Fig. 1. Fetal premature beat. Simultaneously recorded fetal phonocardiogram (upper tracing) and electrocardiogram (lower tracing). ES, ventricular premature beat.
trup Micro Equipment (Radiometer, Copenhagen). During our investigations, we found 5 cases of fetal arrhythmia. On one occasion using the loading test recommended by Ron and Wohlgemuth/ we observed fetal premature beats and arrhythmia. In a further 4 cases, rhythmic disturbances developed during delivery and persisted until the end of the delivery.
Results
The results of our investigations are summarized in Table I. Two of the more interesting cases will be described in detail. Case reports Case 1. Mrs. M. Gy., aged (Case 4, Table I) . This was and the patient was admitted because of premature rupture
35, is a multipara a term pregnancy to our d epartment of the membranes.
Volume 99 Number 1
Significance of fetal arrhythmia
81
Fig. 2. Fetal quadrigeminy. Simultaneously recorded fetal phonocardiogram (upper tracing) and electrocardiogram (lower tracing). ES, ventricular premature beat.
M
M
Fig. 3. Fetal bigeminy. Synchronously recorded fetal electrocardiogram from the maternal abdominal wall (upper tracing) and phonocardiogram (lower tracing). F, fetal; M, maternal complexes.
The fetal heart sounds were rhythmical with a frequency of 130 per minute. Uterine contractions started spontaneously 8 hours after the rupture of the membranes, whereupon fetal arrhythmia appeared, and, therefore, continuous observations were made of fetal heart function and acid-base balance during the remainder of labor. From the picture obtained using a vaginal electrode (Fig. 1) it can be seen that the rhythm was disturbed by premature ventricular beats; the extra complexes were split, broadened, and biphased. Clear amniotic fluid was voided through a catheter introduced into the amnion cavity and its pH value together with
that of the scalp blood was within normal physiologic values. Continuous observations '.vere made for a further 5 hours, 20 minutes, until the end of the delivery. Heart function remained arrhythmic during the later stages of labor but the irregular premature beats were replaced here and there by quadrigeminal pulse (Fig. 2). During this stage of labor, the pH values of the amniotic fluid and scalp blood were within normal physiologic limits. The mother was not given drugs during labor. The newborn infant weighed 3,500 grams and had an Apgar score of 9. The pH values of the blood from the umbilical artery and vein were normal. Premature
82
Septcmb<·t 1, J'H;·;
Kom6romy et al.
'\m . .J . Oh!'t .
~ < ;~· n r·t
t
M
M , J
~'\...I1 ,I
I
y
ES Fig. 4. Fetal trigeminy. Synchronously recorded fetal electrocardiog ram from the maternal abdominal wall ( upper tracing ) and phonocardiogram (low er tracing ) . F. fet al: M. matl"rnal complexes; ES, supraventricular premature bear.
1 sec
Fig. 5. Fetal arrhythmia and premature beat. Synchronously recorded fetal electrocardiogram (upper tracing) and phonocardiogram (lower tracing). ES, supraventricular premature beat.
ventricular beats were detected only occasionally in the newborn. Forty-eight hours after delivery the heart function was normal with no cardiac murmur and the condition of the newborn was faultless. Case 2. Mrs. B. N. Gy., aged 21, is a multipara (Case 5, Table I ). This was a term pregnancy and the patient was transferred to our
clinic from the Maternity Home when fetal arrhythmia was detected during the first stage of parturition. Continuous complex recordings were begun immediately. The ECG record from the maternal abdominal wall revealed irregularly occuring premature supraventricular beats alternating with bigeminy ( Fig. 3) and trigeminy (Fig. 4 ). The form of thP extra complex did not
Significance of fetal arrhythmia
Volume 99 Number I
83
Fig. 6. Fetal bradycardia and premature beat. Synchronously recorded fetal electrocardiogram (upper tracing) and phonocardiogram (lower tracing ) . ES, interpolated premature beat.
~
I
~...... H.. .- ..... . ~
Fig. 7. Fetal arrhythmia. Synchronously recorded fetal electrocardiogram (upper tracing ) and phonocardiogram (lower tracing) .
differ from the others. The amniotic fluid was clear and its pH value as well as that of the scalp blood was normal. Obsetvations were continued for 7 hours, 20 minutes, until the end of the delivery. Arrhythmia increased during labor. In the vaginally recorded ECG arrhythmia, compensated premature supraventricular beats could be observed (Fig. 5) . After it interpolated premature beats appeared in deep bradycardia ( 70 per minute ) (Fig. 6) and immediately before delivery a very serious arrhythmia devel-
oped (Fig. 7). Despite all this the ammottc fluid remained clear and its pH value together with that of the scalp blood was normal. The patient was not given drugs during labor. The newborn infant weighed 3,050 grams and was in good general condition (Apgar score 10 ). The pH values of blood taken from the umbilical cord was within the normal limits. The ECG of the newborn infant revealed premature beats of several foci and a sinoauricular block which remained in an alternating form for 21 days after
84
~t'ph·mlw:
Kom6romy et ol. \tiL
delivery. During this period, the general condition of the infant was faultl<'ss and a detaih'd pediatric examination found no heart disease. At the age of 4 months the infant's heart function was regular.
Comment
Salingn recommended examination of capillary blood from the scalp to determine fetal intrauterine acidosis. The actual pH value of the blood is the resultant of the factors maintaining acid-base balance. From a clinical viewpoint, its determination in itself affords suitable information about the momentary condition of the fetus and is much more reliable than the measuring of the p0 2 •8 Though Rooth, Sjostedt, and Caligara, 9 and Schreiner1 " have shown that the pH value of the amniotic fluid also provides information on gaseous exchange in the fetus (in certain cases we ourselves have found it so3 ) so far this problem has not been settled.n In our investigations of fetal heart function and gaseous exchange we were able to show that in the cases we examined arrhythmia was not correlated with acidosis. This was further borne out by measurement of the pH value of the umbilical cord blood immediately after delivery and the good general condition of the newborn. Hon~ has suggested that in arrhythmia characterized by irregularly occurring premature beats the disorder of the exciting and conducting system of the heart is due to an increased vagus tonus. In the cases we examined) the amniotic fluid did not contain meconium and the mnbilical cord was not twisted around the shoulders or neckthese being conditions in which the role of the vagus would be markedly emphasized. According to Unghvary, 1 " multiple foci
f
()h..,t,
l, 19~·i7 & (;~II("'~
premature beat~, or bi--. tri·, and yuadn~em mal pulse in adults are frequently of myocardial origln: but we have been unable to find any report dealing with similar permanent fetal arrhythmia in the literature. Freistadt 1 " reported a case of transient fetal bigeminy, but the newborn had no heart disease. In Case 5 (Table Il we first thought that the arrhythmia might be due to a cono-enital disorder of the excitation and con" ducting system of the heart, but we were unable to demonstrate cardiac disease in the newborn. Our data support the view that arrhythmia caused by premature beats is more frequent during delivery than during pregnancy. It appears to be a transient functional disorder (increased vagus tonus?) which generally disappears after delivery. However, one report 14 in the literature suggests that premature heartbeats may be caused by congenital malformation of the heart. Our own results suggest that such arrhythmia, whether due to an increased vagus tonus or a heart defect, does. n~t require intervention as this arrhythmia m itself is not a sign of fetal distress. In our present study the interdependence of fetal heart rate and acid-base balance was investigated in a special field. The detailed analysis of this interdependence in different clinical situations comprises the further objectives for study. We hereby express our gratitude to Dr. E. H. Hon, Yale University, N'ew Haven, Connecticut, for placing the vaginal electrode wnstructed by him at our disposal, and to our colleague Dr. T. Kaszas, University Department of Pediatrics, Debrecen, for his very gerwrous help in thl' checkup of the newborn.
REFERENCES
1. Redman, T. F.: J. Obst. & Gynaec. Brit. Emp. 65: 304, 1958.
2. Ron, E. H., and Huang, H. S.: Obst. & Gynec. 20: 81, 1962. . 3. Suranyi, s., Gaal, J., Komaromy B., M!ltaly, Gy., Mocsary, P., and Pohanka, 0.: Lancet 1: 744, 1966,
4. Komliromy, B., Gaal, J., Mihaly_, Gy., Mocsary, P., Pohanka, 0., an
Volume 99 Number I
7. Hon, E. H., and Wohlgemuth, R.: AM. J. 0BST. & GYNEG. 81; 361, 1961. 8. Saling, E.; Das Kind im Bereich der Geburtshilfe, Stuttgart, 1966, Georg Thieme Verlag. 9. Rooth, G., Sjostedt, S., and Caligara, F.: AM. J. 0BST. & GYNEC. 81: 4, 1961. 10. Schreiner, W. F.: Fruchtwasser und Fetus, Basel/New York, 1964, S. Karger, AG.
Significance of fetal arrhythmia
85
11. Rooth, G., and Sjovall, A.: Lancet 2: 371, 1966. 12. Unghvary, L.: KHnikai es kiserleti elektrokardiographia, Budapest 1958, Medicina. 13. Freistadt, H.: AM.]. 0BST. & GYNEC. 84: 13, 1962. 14. Dippel, A. L.: AM. J. OssT. & GYNEC. 27: 120, 1934.