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Quantitative studies in fetal electrocardiography
Quantitative studies in fetal electrocardiography Ill. Comparison of breech and cephalic presentation data; endocrine basis for fetal rotation, a hypothesis
SAUL D. LARKS, PH.D. AUGUSTA WEBSTER, M.D. GOLDA G. LARKS, B.S. Columbia, Missouri, and Chicago, Illinois
On the basis of qualitative and quantitative studies, it is shown that, while the diagnosis of cephalic presentation is quite possible from the fetal electrocardiogram (EGG), the diagnosis of breech presentation is restricted. Fetal EGG amplitudes are shown to be smaller for breech presentations in general as compared with cephalic presentations. An anomalous reversal of magnitudes of EGG values is shown for the breech presentation, with the SN values for the female, for example, being larger than for the male. Regression equations identify the phenomenon and provide a quantitative description. On the basis of these findings, a hypothesis is proposed for an endocrine basis for fetal rotation. An endocrine mechanism is proposed, which, if blocked, leads to persistent breech presentation and breech delivery.
A S Y E T , T H E M E C H A N I S M which assures the optimal cephalic presentation for delivery is not understood. Vartan 7• 8 put the question thus: "the fundamental problem of why the foetus should present by the head rather than by the breech is one which still awaits solution." Even so today. Among many theories, that of a kind of mechanical accommodation of the fetus to the pyriform uterus is perhaps most frequently cited. In the course of the bioelectric investigations undertaken by this laboratory,Z· 5 it has been shown that a sex difference exists in certain fetal ECG amplitudes as well as in the ECG's of the newborn infant.G Thus, the fetal R wave is larger in the case of the female fetus, and it was suggested that fetal
and newborn ECG data, such as the R wave or the S wave, might serve as an index to long-term genetic-endocrine state. The substantial experience of this laboratory in comparable bioelectric studies in breech deliveries forms the basis of this report; it will be shown that the anomalous ECG values recorded suggest a concept for the mechanism of the normal breech-cephalic rotation as well as an explanation for the persistent breech delivery. The fetal ECG patterns in breech presentations will be analyzed both qualitatively and quantitatively. It is believed that such analysis may help to clarify some of the problems of the field. The growth of the interest1 indicates that information derived from fetal studies is becoming part of the armamPntorium of the obstetrician.
From the Department of Veterinary Physiology and Pharmacology and Department of Obstetrics and Gynecology, the University of Missouri, Columbia, Missouri, and the Department of Obstetrics, Cook County Hospital and Northwestern University, Chicago, Illinois.
Materials and methods During the period from October, 1962, through April, 1966, studies of fetal physiology, the fetal ECG, and the birth process
282
Volume 103 Number 2
Effect of presentation on FECG
c I 20°
I8 0 o
283
breech deliveries. Student's t tests comparing the means were done, as were correlation studies. Fig. 1 serves to illustrate the effect of breech inversion on typical fetal ECG and electrical axis values and shows in addition the effect of right axis shift for the breech and cephalic cases.
Af :+------7
/A'!
l5
180°Af
D
120°
Fig. 1. Effect of presentation on apparent fetal EGG and electrical axis value. A, Breech presentation, normal axis value. Actual values, R = 10, S = 5, Ar 120 degrees. Because of breech inversion, apparent values are S' = 10, R' = 5, and Ar' 180 degrees. The fetal EGG in the usual breech presentation thus shows pronounced negative Q or S waves. Frequency of occurrence, 90 per cent of breech cases. B, Breech presentation, right axis shift. Actual values, R 5, S 10, A1 180 degrees. Because of breech inversion, apparent values are S' = 5, R' = 10, Ar' = 120 degrees. Thus, if breech presentation and right axis shift in the fetal heart coexist, pronounced positive signals, with R' greater than S' will be seen, and the apparent electrical axis may be in the vicinity of 120 degrees. Frequency of occurrence, 5 to 10 per cent of breech cases. C, Cephalic presentation, normal axis value. R = 10, S = 5, Ar = 120 degrees. Predominant positive complexes will be seen. Frequency of occurrence, 70 per cent of cephalic cases. D, Cephalic presentation, right axis shift. R 5, S or Q = 10, Ar = 180 degrees. Predominant negative complexes will be seen. Frequency of occurrence, 30 per cent of cephalic cases.
=
=
=
=
=
=
have been made at Cook County General Hospital in Chicago, encompassing some 5,000 pregnancies. 3 • 4 The breech deliveries of that period form one of the subgroups studied in this work. In each case, fetal ECG's were recorded during labor, and standard ECG's recorded on all liveborns. The Magnavox fetal electrocardiograph was used for the fetal studies, utilizing a pass band from 0.1 to 100 cycles. Initial electrode placement for fetal ECG work was midline, upper-electrode positive. Data were entered on punch cards, and processed on an I.B.M. 7040 digital computer system. Analysis was made comparing male and female fetuses in the singleton cephalic comparison group, as well as in the
Results
Fetal ECG patterns in breech presentations. Fig. 2 shows the usual appearance of the fetal ECG in breech presentations, showing (as in 2, A, B, and C) that the complex is usually negative. However, it should be noted that occasional positivity of the fetal complex with the breech is not excluded, as in Fig. 2, D. For comparison, Fig. 2, E and F shows the appearance of the fetal ECG in cephalic presentations; it is observed that positive, diphasic, and also negative complexes may be seen. Since a negative complex may be seen in both cephalic and breech presentations, it is desirable to know the frequency of occurrence of typical complexes in both the cephalic and breech presentation, and this is done in Fig. 3, on the apparent electrical axis basis. Thus, predominantly positive complexes will correspond to electrical axes markedly less than 150 degrees, whereas predominantly negative complexes will correspond with electrical axes greater than 150 degrees. Where diphasic complexes show R = S, the apparent electrical axis is 150 degrees. It is observed that the complexes in breech presentations are, indeed, markedly negative. But, it is also observed that 32 per cent of the cephalic presentations, totalling 579 cases, also show negative complexes. Data comparison-cephalic and breech. In Table I, a statistical comparison is made for total cephalic vs. total breech presentations, and it is seen that the bioelectric values, for peak-to-peak amplitude, for Rr and Sr, and for fetal cardiac electrical axis, are all smaller, significantly, in the case of the breech. It may be noted that the maternal systolic blood pressure is elevated m mothers carrying a persistent breech.
284
Larks/ Webster/ and Larks
\Jll.
Januaq Fl. 19-t/1 Ohst. & (;":·nee
J.
A
c
D
E
F
Fig. 2. Fetal ECG's; F, fetus. A, B, C, Breech presentations showing predominantly negative complexes. D, The exceptional breech presentation associated with a positive complex. E, The typical positive complex associated with a cephalic presentation. F, The negative complex seen in those cephalic presentations associated with electrical axis values greater than 160 degrees.
Fetal and newborn ECG values in breech presentations. As reference, Fig. 4, A shows the s"' values for male and female in the usual cephalic presentation, showing the marked sex difference as reported. Fig. 4, B shows the case for the male breech, and it is seen that the values are much smaller than
expected. Fig. 4, C shows the case for the female breech, and here it is seen that the s:"if average value is much larger than expected. Hence, a type of anomalous or unexpected reversal of values is shown for the male and female breeches. Since it might be argued initially that the
Volume 103 Number 2
Effect of presentation on FECG
Cases
Distribution of Electrical Axes
285
> 160" \00
100 Cephalic
...
80
80
"
0
~
..
s:; 0.
N = 876
0
~
I-
.
60 'E
Cephalic singles, 1773 cases
60
40
u
~ 40
N =579
0
oe
N =318
20
0 100
I Breech sgls,49 1 I
N =45
I I
..il:
80
80
60
60
"
0 s:;
~
e
~"
-
.... c:
m
~
40
40
a.
0
oe
20
Breech
20
N=4 N=O
0
~1o4•
105 -150°
> 150°
(R>>S, Q)
(R>S, Q)
(S,Q>Rl
AF- Electrical Axes
Fig. 3. Distribution of electrical axis values. Above, cephalic presentations; below, breech presentations.
Table I. Data comparison: cephalic vs. breech* Cephalic, N Variable Weeks gestation Fetal arnplitude Birth weight Duration, ms RF (JLV) s., (JLV)
AF AN M.S. Pr. M.D. Pr.
Mean
I
S.D.
=
818
I
Breech, N
Std. error
Mean
I
S.D.
=
48
I
37.3
3.2
0.11
36.5
3.8
0.55
32.3 111 47.6 19 12.3 134.8 131.7 116.7 74.2
20.8 18.1 7.4 13.6 9.5 25.3 34.2 10.3 7.4
0.7 0.6 0.26 0.5 0.3 0.8 1.1 0.4 0.26
25.1 103 45.2 15.5 8.8 123.5 123.8 122.7 76.3
18.9 22 8.3 10.7 10.5 26.2 31.3 17.8 10.9
2.7 3.1 1.2 1.5 1.5 3.7 4.5 2.6 1.6
*Breech fetal ECG amplitudes values were inverted for purposes of this comparison.
t+,
Std. error
significant; -, not significant.
t
Significance
1.43 2.58 2.50 1.97 2.20 2.25 2.95 1.72 -2.34 -1.31
+t + + + + + +
286 Larks, Webster, and Larks :\m .
Jauuary 1.); 1%~) Ohst. & (;yn<'c.
.T.
SN , Microvolts
244
180
221
Cephalic, singletons
A male cephalic
female cephalic
Avg.
190
244
B ..__ __.__ _...__-e~---'----'---"--_,__ _..,_ _.__ _...__~. Male breech, singletons male breech
male cephalic
c
260 180 _ _..__ __.__ _..__ __.__ _..__ __.__ _..__ _.,___..__ Female breech, singletons female breech female cephalic
...__~
Fig. 4. Values for SN, the S wave of Lead II of the newborn electrocardiogram. A, the sex difference in mean SN values, in cephalic singletons. B, comparison of Sx values for the male cephalic and male breech. C, comparison of S, values for the female cephalic and f,.male breech.
0
Female
Male
Cephalic Singletons
Female
Male
Breech Singletons
Fig. 5. The ratio s,/weight (f.lv/oz.) for cephalic singletons and breech singletons.
larger SN value for the male cephalic as compared with the female cephalic reflects only a possible average weight difference, a new variable was developed, SN/weight for each case. It it were true, in fact, that SN values were merely a function of weight, the
ratio SN/weight should be constant, and should show no sex difference. Fig. 5 shows that this is not the case. The bar graph comparing SN/weight is a rather specific measure of a factor which distinguishes the male fetus from the female fetus, hence presumably an
Effect of presentation on FECG 287
Volume 103 ~umber
2
index to endocrine state. A larger SN/weight value level suggests an androgenic effect. If now this factor SN/weight be utilized for the breeches, as in Fig. 5, the anomalous reversal of values is seen again, with the female breech showing larger values than the male breech. Regression data. In the earlier work of this laboratory, it was indicated that the SN wave could be used as an index to longterm endocrine state. It was also shown that multivariate linear regression techniques could be used for the purpose of identification of significant factors. Hence, regression equation prediction of SN waves was used for cephalic and for breech presentation groups in the effort to search for such factors. Results. Predictions for SN, the newborn S wave of Lead II, comparing cephalic presentations and breech presentations: Cephalic: y = 316.6 + 1.26 (fetal) +0.12 (BW) + 8.5 (SF) + 2.4 (AF) + 0.48 (M.S.Pr.) + 8.6 (f.h.t.) - 24.3 (sex) - 5.7 (RF) - 19 (brady.)- 47 (NI) - 6.7 (complex) R = 0.56 S.E. = 214.3 Breech:
y = - 215 + 0.9 (BW) + 60.7 (sex) + 7.3 (RF) + 26.8 (f.h.t.)
- 3.5 (fetal) - 8.9 (Gr.) R = 0.46 S.E. = 191.7. Comment
The typical fetal ECG in breech presentations. It is observed, as in Fig. 2, that the typical fetal ECG in a breech presentation, recorded with midline electrodes, does indeed show a negative complex in general, as might be expected from the upright fetal position. It is also observed, in Fig. 3, that the bulk of breech cases show such negativegoing complexes. Yet, the possibility of diagnosis of the breech presentation from the fetal ECG alone is quite another matter, and must be approached with care and with quantitative technique. Examination of the Fig. 3 data for the cephalic cases shows that 32 per cent of the cases, numerically 5 79 cases in this series,
will have electrical axes greater than 150 degrees and thus S waves greater than R waves, frequently much greater. Hence, on a quantitative basis, predominantly S wave (or Q wave) configurations will correspond with cephalic presentation in 90 per cent of the instances, and with breech presentation in 45 to 50 cases or about 10 per cent of the instances. Hence, overstatements of the ability to diagnose the breech presentation solely on the basis of the fetal ECG, or on the basis of concordance with the maternal complex, do not correspond with reality. There is, indeed, much presentation information in the fetal ECG, which should be used with care, on the basis of quantitative information and broad experience. If a clear criterion of electrical axes greater than, or smaller than, 160 degrees is used, the following summary may be made: 1. Complexes which are markedly positive (directed upward in our system) or whose net value is positive, are associated with vertex, cephalic presentations-reliability about 99 per cent. 2. Complexes which are markedly negative are associated with either vertex cephalic presentation, plus fetal cardiac electrical axes greater than 160 degrees (about 85 per cent of such cases, or breech presentations (about 15 per cent) . 3. Leaving out the noninformative cases (absent complex), breech presentations are associated with negative complexes-reliability about 90 per cent). Certainly, in the absence of any other information, demonstration of a negative complex in the fetal ECG should receive attention, since it would be consistent with breech presentation, or with right axis shift in a cephalic presentation. Mean values. In Table I it is seen that mean values for the peak-to-peak fetal amplitude, as well as individual R and S components, are smaller in the case of the breech, and that a comparison with the mean cephalic values shows that the difference is significant statistically. The full significance of the smaller value in the case of the breech is not as yet apparent, but it does have the
288 Larks, Webster, and Larks
practical significance that more of the ECG recordings with the breeches are noninformative, i.e., complexes might more often, not be identifiable. Correlation studies show the following significant correlations: 1. There is a greater than usual probability of breech presentations among twins-r = 0.68; 2. The fetal ECG's with breeches are more likely to be noninformative (see above)r = 0.47; 3. Infants born as breech presentations show an increased probability of death within two years-r = 0.29 4. The breeches show a smaller mean birth weight-r = 0.19; 5. Breech presentation newborns show smaller electrical axes (to the left) - r = 0.17; 6. Correlation is shown with relatively low Apgar ratings-r = 0.17-and with early delivery-r = 0.1. Anomalous SN values in the breech presentation. Considerable interest attaches to the showing that a type of anomalous SN value occurs in the breech presentations. In a previous report from this laboratory 6 it was shown that a sex difference existed in SN values as between the male and female, with the male newborn showing significantly larger values, 244 > 180 0V. It was then proposed that the SN value could be considered as an index to long-term endocrine state, i.e., that relatively large SN values could be consistent with androgenic effects, as in the male. Similar considerations apply to the suggested SN/weight ratio. In this light, consideration of the breech SN values leads to some interesting possibilities. The male breech values are smaller than expected, 190 > 244, suggesting inadequate androgenic action (or excessive estrogenic action). The SN values for the male breech are of the order of magnitude and comparable to those of the normal female cephalic, 190 '"'"' 180. The female breech mean value for SN is larger than expected, 260 > 180, suggesting exposure to excessive androgenic action.
.\m.
January 15, 1%') Obst. & Gyncc.
J.
This mean S:-< value for the female breech is of the order of magnitude and comparable to those of the normal male cephalic 260 ~ 244. If, therefore, the persistent breech presentation fetus shows a heart which reflects an unusual endocrine milieu, it is reasonable tn assume that the breech presentation itself is the n~sult of that same unusual endocrine milieu. Analysis and comparison of the regression equations predicting the s:'< waves for the cephalic presentations and for the breech presentations makes possible a demonstration of considerable interest. It should be borne in mind that a principal use of such equations is the possible identification or significant factors, as well as the clin•ction of their effect. With attention first directed to the n~ gression equation for sl'\ in the case of cephalic presentations, it is seen that the factor, sex, is a significant factor, and that the sign of its regression coefficient is negative. Sinn· the coding used for the variable sex was, male, l, and female, 2, it is seen that for the female the predicted s;\1 vvould lw smaller by 24.3 units or microvolts than would he the case for a male; this pr~diction is in ac·· cordance with the smaller sl'\ values observed for the normal cephalic presentation female·. Inspection of the regression case for the breech presentations reveals that, again, the variable, sex, is a significant factor, but this time the sign of the regression coefficiem j, positive; hence, now. the female, coded 2. will have a predicted S~'~ value some 60 ttV greater than that for the male. The regression equations thus clearly show the reversal phenomenon in the case of the breech presentations. It is in order, therefore, to propose the following concepts to explain the data presented, as supporting a hypothesis for the~ endocrine basis for fetal rotation: l. Fetal rotation about a trans\·erse axis, i.e., the normal breech-cephalic rotation in early gestation, takes place under the influence of an optimal endocrine environment. 2. In the case of a male fetus, this normal
Volume 103 ~umber
Effect of presentation on FECG
289
2
rotation may be blocked by excess estrogenic substances (or inadequate androgenic substances) ; the result is a persistent breech presentation, and a fetal heart showing the effects of the abnormal endocrine milieu, in the form of low SN values. 3. In the case of a female fetus, the normal rotation may be blocked by excess androgenic substances; the result is a persistent breech presentation, and a fetal heart showing the effects of the abnormal intrauterine endocrine state in the form of large SN values.
The data presented in this report support the hypothesis of an endocrine basis for fetal rotation. It should be possible, by further investigation, to develop information which would bear upon the validity of the concepts. The support of the computer center staff of the University of Missouri, in particular Mr. Howard Watts and Mr. Jack Naylor, is gratefully acknowledged.
REFERENCES
I. Davis, M. E., and McKeown, M. & Gynec. Surv. 22: 549, 1967.
J.:
Obst.
2. Larks, S.D.: Fetal electrocardiography, Springfield, Illinois, 1960, Charles C Thomas, Publisher. 3. Larks, S. D.: Obst. & Gynec. 24: 1, 1964. 4. Larks, S. D.: AM. J. 0BST. & GYNEC. 91: 46, 1965.
5. Larks, S. D., Webster, A., and Larks, G. G.: AM. J. 0BST. & GYNEC. 98: 52, 1967. 6. Larks, S. D., and Larks, G. G.: AM. J. 0BsT. & GYNEC. 100: 1135, 1968. 7. Vartan, C. K.: Lancet 1:595, 1940. 8. Vartan, C. K.: ]. Obst. & Gynaec. Brit. Emp. 52: 417, 1945.
SAUL D. LARKS, PH.D. AUGUSTA WEBSTER, M.D. GOLDA G. LARKS, B.S. Columbia, Missouri, and Chicago, Illinois
On the basis of qualitative and quantitative studies, it is shown that, while the diagnosis of cephalic presentation is quite possible from the fetal electrocardiogram (EGG), the diagnosis of breech presentation is restricted. Fetal EGG amplitudes are shown to be smaller for breech presentations in general as compared with cephalic presentations. An anomalous reversal of magnitudes of EGG values is shown for the breech presentation, with the SN values for the female, for example, being larger than for the male. Regression equations identify the phenomenon and provide a quantitative description. On the basis of these findings, a hypothesis is proposed for an endocrine basis for fetal rotation. An endocrine mechanism is proposed, which, if blocked, leads to persistent breech presentation and breech delivery.
A S Y E T , T H E M E C H A N I S M which assures the optimal cephalic presentation for delivery is not understood. Vartan 7• 8 put the question thus: "the fundamental problem of why the foetus should present by the head rather than by the breech is one which still awaits solution." Even so today. Among many theories, that of a kind of mechanical accommodation of the fetus to the pyriform uterus is perhaps most frequently cited. In the course of the bioelectric investigations undertaken by this laboratory,Z· 5 it has been shown that a sex difference exists in certain fetal ECG amplitudes as well as in the ECG's of the newborn infant.G Thus, the fetal R wave is larger in the case of the female fetus, and it was suggested that fetal
and newborn ECG data, such as the R wave or the S wave, might serve as an index to long-term genetic-endocrine state. The substantial experience of this laboratory in comparable bioelectric studies in breech deliveries forms the basis of this report; it will be shown that the anomalous ECG values recorded suggest a concept for the mechanism of the normal breech-cephalic rotation as well as an explanation for the persistent breech delivery. The fetal ECG patterns in breech presentations will be analyzed both qualitatively and quantitatively. It is believed that such analysis may help to clarify some of the problems of the field. The growth of the interest1 indicates that information derived from fetal studies is becoming part of the armamPntorium of the obstetrician.
From the Department of Veterinary Physiology and Pharmacology and Department of Obstetrics and Gynecology, the University of Missouri, Columbia, Missouri, and the Department of Obstetrics, Cook County Hospital and Northwestern University, Chicago, Illinois.
Materials and methods During the period from October, 1962, through April, 1966, studies of fetal physiology, the fetal ECG, and the birth process
282
Volume 103 Number 2
Effect of presentation on FECG
c I 20°
I8 0 o
283
breech deliveries. Student's t tests comparing the means were done, as were correlation studies. Fig. 1 serves to illustrate the effect of breech inversion on typical fetal ECG and electrical axis values and shows in addition the effect of right axis shift for the breech and cephalic cases.
Af :+------7
/A'!
l5
180°Af
D
120°
Fig. 1. Effect of presentation on apparent fetal EGG and electrical axis value. A, Breech presentation, normal axis value. Actual values, R = 10, S = 5, Ar 120 degrees. Because of breech inversion, apparent values are S' = 10, R' = 5, and Ar' 180 degrees. The fetal EGG in the usual breech presentation thus shows pronounced negative Q or S waves. Frequency of occurrence, 90 per cent of breech cases. B, Breech presentation, right axis shift. Actual values, R 5, S 10, A1 180 degrees. Because of breech inversion, apparent values are S' = 5, R' = 10, Ar' = 120 degrees. Thus, if breech presentation and right axis shift in the fetal heart coexist, pronounced positive signals, with R' greater than S' will be seen, and the apparent electrical axis may be in the vicinity of 120 degrees. Frequency of occurrence, 5 to 10 per cent of breech cases. C, Cephalic presentation, normal axis value. R = 10, S = 5, Ar = 120 degrees. Predominant positive complexes will be seen. Frequency of occurrence, 70 per cent of cephalic cases. D, Cephalic presentation, right axis shift. R 5, S or Q = 10, Ar = 180 degrees. Predominant negative complexes will be seen. Frequency of occurrence, 30 per cent of cephalic cases.
=
=
=
=
=
=
have been made at Cook County General Hospital in Chicago, encompassing some 5,000 pregnancies. 3 • 4 The breech deliveries of that period form one of the subgroups studied in this work. In each case, fetal ECG's were recorded during labor, and standard ECG's recorded on all liveborns. The Magnavox fetal electrocardiograph was used for the fetal studies, utilizing a pass band from 0.1 to 100 cycles. Initial electrode placement for fetal ECG work was midline, upper-electrode positive. Data were entered on punch cards, and processed on an I.B.M. 7040 digital computer system. Analysis was made comparing male and female fetuses in the singleton cephalic comparison group, as well as in the
Results
Fetal ECG patterns in breech presentations. Fig. 2 shows the usual appearance of the fetal ECG in breech presentations, showing (as in 2, A, B, and C) that the complex is usually negative. However, it should be noted that occasional positivity of the fetal complex with the breech is not excluded, as in Fig. 2, D. For comparison, Fig. 2, E and F shows the appearance of the fetal ECG in cephalic presentations; it is observed that positive, diphasic, and also negative complexes may be seen. Since a negative complex may be seen in both cephalic and breech presentations, it is desirable to know the frequency of occurrence of typical complexes in both the cephalic and breech presentation, and this is done in Fig. 3, on the apparent electrical axis basis. Thus, predominantly positive complexes will correspond to electrical axes markedly less than 150 degrees, whereas predominantly negative complexes will correspond with electrical axes greater than 150 degrees. Where diphasic complexes show R = S, the apparent electrical axis is 150 degrees. It is observed that the complexes in breech presentations are, indeed, markedly negative. But, it is also observed that 32 per cent of the cephalic presentations, totalling 579 cases, also show negative complexes. Data comparison-cephalic and breech. In Table I, a statistical comparison is made for total cephalic vs. total breech presentations, and it is seen that the bioelectric values, for peak-to-peak amplitude, for Rr and Sr, and for fetal cardiac electrical axis, are all smaller, significantly, in the case of the breech. It may be noted that the maternal systolic blood pressure is elevated m mothers carrying a persistent breech.
284
Larks/ Webster/ and Larks
\Jll.
Januaq Fl. 19-t/1 Ohst. & (;":·nee
J.
A
c
D
E
F
Fig. 2. Fetal ECG's; F, fetus. A, B, C, Breech presentations showing predominantly negative complexes. D, The exceptional breech presentation associated with a positive complex. E, The typical positive complex associated with a cephalic presentation. F, The negative complex seen in those cephalic presentations associated with electrical axis values greater than 160 degrees.
Fetal and newborn ECG values in breech presentations. As reference, Fig. 4, A shows the s"' values for male and female in the usual cephalic presentation, showing the marked sex difference as reported. Fig. 4, B shows the case for the male breech, and it is seen that the values are much smaller than
expected. Fig. 4, C shows the case for the female breech, and here it is seen that the s:"if average value is much larger than expected. Hence, a type of anomalous or unexpected reversal of values is shown for the male and female breeches. Since it might be argued initially that the
Volume 103 Number 2
Effect of presentation on FECG
Cases
Distribution of Electrical Axes
285
> 160" \00
100 Cephalic
...
80
80
"
0
~
..
s:; 0.
N = 876
0
~
I-
.
60 'E
Cephalic singles, 1773 cases
60
40
u
~ 40
N =579
0
oe
N =318
20
0 100
I Breech sgls,49 1 I
N =45
I I
..il:
80
80
60
60
"
0 s:;
~
e
~"
-
.... c:
m
~
40
40
a.
0
oe
20
Breech
20
N=4 N=O
0
~1o4•
105 -150°
> 150°
(R>>S, Q)
(R>S, Q)
(S,Q>Rl
AF- Electrical Axes
Fig. 3. Distribution of electrical axis values. Above, cephalic presentations; below, breech presentations.
Table I. Data comparison: cephalic vs. breech* Cephalic, N Variable Weeks gestation Fetal arnplitude Birth weight Duration, ms RF (JLV) s., (JLV)
AF AN M.S. Pr. M.D. Pr.
Mean
I
S.D.
=
818
I
Breech, N
Std. error
Mean
I
S.D.
=
48
I
37.3
3.2
0.11
36.5
3.8
0.55
32.3 111 47.6 19 12.3 134.8 131.7 116.7 74.2
20.8 18.1 7.4 13.6 9.5 25.3 34.2 10.3 7.4
0.7 0.6 0.26 0.5 0.3 0.8 1.1 0.4 0.26
25.1 103 45.2 15.5 8.8 123.5 123.8 122.7 76.3
18.9 22 8.3 10.7 10.5 26.2 31.3 17.8 10.9
2.7 3.1 1.2 1.5 1.5 3.7 4.5 2.6 1.6
*Breech fetal ECG amplitudes values were inverted for purposes of this comparison.
t+,
Std. error
significant; -, not significant.
t
Significance
1.43 2.58 2.50 1.97 2.20 2.25 2.95 1.72 -2.34 -1.31
+t + + + + + +
286 Larks, Webster, and Larks :\m .
Jauuary 1.); 1%~) Ohst. & (;yn<'c.
.T.
SN , Microvolts
244
180
221
Cephalic, singletons
A male cephalic
female cephalic
Avg.
190
244
B ..__ __.__ _...__-e~---'----'---"--_,__ _..,_ _.__ _...__~. Male breech, singletons male breech
male cephalic
c
260 180 _ _..__ __.__ _..__ __.__ _..__ __.__ _..__ _.,___..__ Female breech, singletons female breech female cephalic
...__~
Fig. 4. Values for SN, the S wave of Lead II of the newborn electrocardiogram. A, the sex difference in mean SN values, in cephalic singletons. B, comparison of Sx values for the male cephalic and male breech. C, comparison of S, values for the female cephalic and f,.male breech.
0
Female
Male
Cephalic Singletons
Female
Male
Breech Singletons
Fig. 5. The ratio s,/weight (f.lv/oz.) for cephalic singletons and breech singletons.
larger SN value for the male cephalic as compared with the female cephalic reflects only a possible average weight difference, a new variable was developed, SN/weight for each case. It it were true, in fact, that SN values were merely a function of weight, the
ratio SN/weight should be constant, and should show no sex difference. Fig. 5 shows that this is not the case. The bar graph comparing SN/weight is a rather specific measure of a factor which distinguishes the male fetus from the female fetus, hence presumably an
Effect of presentation on FECG 287
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index to endocrine state. A larger SN/weight value level suggests an androgenic effect. If now this factor SN/weight be utilized for the breeches, as in Fig. 5, the anomalous reversal of values is seen again, with the female breech showing larger values than the male breech. Regression data. In the earlier work of this laboratory, it was indicated that the SN wave could be used as an index to longterm endocrine state. It was also shown that multivariate linear regression techniques could be used for the purpose of identification of significant factors. Hence, regression equation prediction of SN waves was used for cephalic and for breech presentation groups in the effort to search for such factors. Results. Predictions for SN, the newborn S wave of Lead II, comparing cephalic presentations and breech presentations: Cephalic: y = 316.6 + 1.26 (fetal) +0.12 (BW) + 8.5 (SF) + 2.4 (AF) + 0.48 (M.S.Pr.) + 8.6 (f.h.t.) - 24.3 (sex) - 5.7 (RF) - 19 (brady.)- 47 (NI) - 6.7 (complex) R = 0.56 S.E. = 214.3 Breech:
y = - 215 + 0.9 (BW) + 60.7 (sex) + 7.3 (RF) + 26.8 (f.h.t.)
- 3.5 (fetal) - 8.9 (Gr.) R = 0.46 S.E. = 191.7. Comment
The typical fetal ECG in breech presentations. It is observed, as in Fig. 2, that the typical fetal ECG in a breech presentation, recorded with midline electrodes, does indeed show a negative complex in general, as might be expected from the upright fetal position. It is also observed, in Fig. 3, that the bulk of breech cases show such negativegoing complexes. Yet, the possibility of diagnosis of the breech presentation from the fetal ECG alone is quite another matter, and must be approached with care and with quantitative technique. Examination of the Fig. 3 data for the cephalic cases shows that 32 per cent of the cases, numerically 5 79 cases in this series,
will have electrical axes greater than 150 degrees and thus S waves greater than R waves, frequently much greater. Hence, on a quantitative basis, predominantly S wave (or Q wave) configurations will correspond with cephalic presentation in 90 per cent of the instances, and with breech presentation in 45 to 50 cases or about 10 per cent of the instances. Hence, overstatements of the ability to diagnose the breech presentation solely on the basis of the fetal ECG, or on the basis of concordance with the maternal complex, do not correspond with reality. There is, indeed, much presentation information in the fetal ECG, which should be used with care, on the basis of quantitative information and broad experience. If a clear criterion of electrical axes greater than, or smaller than, 160 degrees is used, the following summary may be made: 1. Complexes which are markedly positive (directed upward in our system) or whose net value is positive, are associated with vertex, cephalic presentations-reliability about 99 per cent. 2. Complexes which are markedly negative are associated with either vertex cephalic presentation, plus fetal cardiac electrical axes greater than 160 degrees (about 85 per cent of such cases, or breech presentations (about 15 per cent) . 3. Leaving out the noninformative cases (absent complex), breech presentations are associated with negative complexes-reliability about 90 per cent). Certainly, in the absence of any other information, demonstration of a negative complex in the fetal ECG should receive attention, since it would be consistent with breech presentation, or with right axis shift in a cephalic presentation. Mean values. In Table I it is seen that mean values for the peak-to-peak fetal amplitude, as well as individual R and S components, are smaller in the case of the breech, and that a comparison with the mean cephalic values shows that the difference is significant statistically. The full significance of the smaller value in the case of the breech is not as yet apparent, but it does have the
288 Larks, Webster, and Larks
practical significance that more of the ECG recordings with the breeches are noninformative, i.e., complexes might more often, not be identifiable. Correlation studies show the following significant correlations: 1. There is a greater than usual probability of breech presentations among twins-r = 0.68; 2. The fetal ECG's with breeches are more likely to be noninformative (see above)r = 0.47; 3. Infants born as breech presentations show an increased probability of death within two years-r = 0.29 4. The breeches show a smaller mean birth weight-r = 0.19; 5. Breech presentation newborns show smaller electrical axes (to the left) - r = 0.17; 6. Correlation is shown with relatively low Apgar ratings-r = 0.17-and with early delivery-r = 0.1. Anomalous SN values in the breech presentation. Considerable interest attaches to the showing that a type of anomalous SN value occurs in the breech presentations. In a previous report from this laboratory 6 it was shown that a sex difference existed in SN values as between the male and female, with the male newborn showing significantly larger values, 244 > 180 0V. It was then proposed that the SN value could be considered as an index to long-term endocrine state, i.e., that relatively large SN values could be consistent with androgenic effects, as in the male. Similar considerations apply to the suggested SN/weight ratio. In this light, consideration of the breech SN values leads to some interesting possibilities. The male breech values are smaller than expected, 190 > 244, suggesting inadequate androgenic action (or excessive estrogenic action). The SN values for the male breech are of the order of magnitude and comparable to those of the normal female cephalic, 190 '"'"' 180. The female breech mean value for SN is larger than expected, 260 > 180, suggesting exposure to excessive androgenic action.
.\m.
January 15, 1%') Obst. & Gyncc.
J.
This mean S:-< value for the female breech is of the order of magnitude and comparable to those of the normal male cephalic 260 ~ 244. If, therefore, the persistent breech presentation fetus shows a heart which reflects an unusual endocrine milieu, it is reasonable tn assume that the breech presentation itself is the n~sult of that same unusual endocrine milieu. Analysis and comparison of the regression equations predicting the s:'< waves for the cephalic presentations and for the breech presentations makes possible a demonstration of considerable interest. It should be borne in mind that a principal use of such equations is the possible identification or significant factors, as well as the clin•ction of their effect. With attention first directed to the n~ gression equation for sl'\ in the case of cephalic presentations, it is seen that the factor, sex, is a significant factor, and that the sign of its regression coefficient is negative. Sinn· the coding used for the variable sex was, male, l, and female, 2, it is seen that for the female the predicted s;\1 vvould lw smaller by 24.3 units or microvolts than would he the case for a male; this pr~diction is in ac·· cordance with the smaller sl'\ values observed for the normal cephalic presentation female·. Inspection of the regression case for the breech presentations reveals that, again, the variable, sex, is a significant factor, but this time the sign of the regression coefficiem j, positive; hence, now. the female, coded 2. will have a predicted S~'~ value some 60 ttV greater than that for the male. The regression equations thus clearly show the reversal phenomenon in the case of the breech presentations. It is in order, therefore, to propose the following concepts to explain the data presented, as supporting a hypothesis for the~ endocrine basis for fetal rotation: l. Fetal rotation about a trans\·erse axis, i.e., the normal breech-cephalic rotation in early gestation, takes place under the influence of an optimal endocrine environment. 2. In the case of a male fetus, this normal
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rotation may be blocked by excess estrogenic substances (or inadequate androgenic substances) ; the result is a persistent breech presentation, and a fetal heart showing the effects of the abnormal endocrine milieu, in the form of low SN values. 3. In the case of a female fetus, the normal rotation may be blocked by excess androgenic substances; the result is a persistent breech presentation, and a fetal heart showing the effects of the abnormal intrauterine endocrine state in the form of large SN values.
The data presented in this report support the hypothesis of an endocrine basis for fetal rotation. It should be possible, by further investigation, to develop information which would bear upon the validity of the concepts. The support of the computer center staff of the University of Missouri, in particular Mr. Howard Watts and Mr. Jack Naylor, is gratefully acknowledged.
REFERENCES
I. Davis, M. E., and McKeown, M. & Gynec. Surv. 22: 549, 1967.
J.:
Obst.
2. Larks, S.D.: Fetal electrocardiography, Springfield, Illinois, 1960, Charles C Thomas, Publisher. 3. Larks, S. D.: Obst. & Gynec. 24: 1, 1964. 4. Larks, S. D.: AM. J. 0BST. & GYNEC. 91: 46, 1965.
5. Larks, S. D., Webster, A., and Larks, G. G.: AM. J. 0BST. & GYNEC. 98: 52, 1967. 6. Larks, S. D., and Larks, G. G.: AM. J. 0BsT. & GYNEC. 100: 1135, 1968. 7. Vartan, C. K.: Lancet 1:595, 1940. 8. Vartan, C. K.: ]. Obst. & Gynaec. Brit. Emp. 52: 417, 1945.