The Significance of the Signs of Fetal Distress

THE SIGNIFICANCE OF THE SIGNS OF FETAL DISTRESS A Preliminary Study SILAS

J. GINSBURG, M.D.,

PHILADELPHIA, PA.

(From the Hospital of the University of Pennsylvania)

U the obstetrician.

NTIL recently, the welfare of the mother has been the main concern of The past few years have seen a greatly increased interest in fetal outcome and in the manifestations of intrauterine fetal jeopardy. In addition to increased infant salvage, the prevention of brain damage has become increasingly important in the mind of the modern obstetrician.

A variety of obstetrical conditions have been mentioned by McCall, 1 Richardson, 2 and othcrs 3 • 4' 5 as the causes of fetal distress. The st11dies of Lillienfeld6 and Latham 7 indicate that fetal hypoxia is one of the causes of irreparable brain damage. Early recognition of the known signs of fetal distress which may indicate sublethal oxygen deprivation should aid in the prevention of this development. There are some instances in which no demonstrable reason for intrapartum jeopardy or even death is discovered. It may be, however, that in all instances the clinical manifestations of fetal distress are at some time sufficiently pronounced for recognition and decisive action. even though the ultimate causes for this distress may not become apparent. As to the heart sounds, recent physiological studies by Barcroft," Greenfield,9 and Reynolds10 have 'shown that fetal distress due to anoxic factors is indicated by bradycardia, with transient or prolonged tachycardia during the recovery. Almost all authors agree as to the grave prognostic significance of a slow fetal heart rate. 1 l-l7 On the other hand, a rise in the rate has been the subject of much controversy. It is considered important by some authors2· 11 ' 14 - 16 and is minimized by others. 3 • 12 • 17 Fluctuation in the fetal heart rate is thought to be important by Beck 15 and by King,1 2 while Abolins 16 is concerned about qualitative changes in fetal heart sounds. As to the significance of meconium, Walker18 points ont that marked hypoxia is necessary to produce this stain in the amniotic fluid, but controversial statements concerning the actual clinical significance of tl1is sign have been made by Hunt, • Adair, 11 and King. 12 DeSoldenhoff 13 and \Vhite 19 feel that meconium staining does not indicate severe distress unless it is accompanied by abnormalities in the fetal heart rate. In general, the newest studies by McCall/ White, 19 DeSoldenhoff,13 and Fitzgerald20 suggest that very few babies die in the process of being born, or shortly thereafter, without first giving detectable warning signs. It is concerning the interpretation of these signs when considered separately and in combination that further information is required to effect an increase in fetal salvage and in subsequent health. Recently, a review of the cesarean sections clone for fetal distress at the Hospital of the University of Pennsylvania 21 was undertaken in the effort to 264

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SIGNIFICANCE OF SIGNS OF FETAL DISTRESS

265

determine the significance of the signs which seemed to warrant the abdominal delivery of patl.ents who were not immediately deliverable per vaginam. Sixty-seven records were studied. Of the 72 babies in this series, 12 per cent were temporarily affected at birth, 7 per cent were stillborn, and 8 per cent succumbed during the neonatal period. A 15 per cent mortality rate occurred despite what, at the time, was considered to be adequate intrapartal observation and prompt intervention, when indicated. It then seemed in order to conduct an intensive study of patients while they were in labor, in the effort to correlate the accepted signs of fetal distress with the condition of the newborn, both at birth and during the postnatal period. A further correlation is attempted between the signs of difficulty and the actual conditions that were found to account for these signs.

Materials and Methods This study encompasses a 6-month period from July 20, 1955, to Jan. 20, 1956. The signs of distress which were selected for this study concerned the fetal heart rate, cardiac arrhythmias, and meconium staining in vertex presentations. The fetal heart tones were recorded at intervals of 15 to 30 minutes (or more often as indicated) in all but 5 per cent of the patients in this series. All who manifested any of the above signs, no matter how transient. were included in the study. The following data as to the signs were also recorded: (1) their relationship to contractions, (2) their duration, (3) the stage of labor in which they appeared, and ( 4) their transience or permanence. Causes found to account for the signs of fetal distress were listed as follows : (1) anatomical factors, including such items as cord and placental accidents, (2) dynamic factors including long labor and cephalopelvic disproportion, and (3) no factor discovered. The immediate neonatal condition is presented as: (1) infant not affected, (2) affected infant, and (3) stillborn infant. An affected infant was one with 3 or more minutes of neonatal apnea, poor muscle tone and color, who required more than the usual means of resuscitation. The condition of the newborn after 4 days was assessed from the point of view of weight loss, respiratory difficulty, neurological disturbance, and feeding problems. This is catalogued as: (1) good, (2) poor, and ( 3) neonatal death. The total deliveries for the time period numbered 1,363, with 152 instances of possible fetal distress, an incidence of 11.2 per cent. The cases fell into the following categories: 1. Meconium staining alone 2. Falling fetal heart rate

77 cases

(including 8 cases with rising also) (a) alone (b) with meconium 3. Rising fetal heart rate (a) alone (b) with mec.onium 4. Fluctuation in rate with meconium

48 cases 33 cases 15 cases

20 cases 11 cases 9 cases 7 cases

Results The age and parity distribution of the patients in this series were the same as those of the general obstetrical population. Prematurity and postmaturity were not significant factors in that length of gestation was 38 to 42 weeks in 93 per cent of patients. Meconium-stained Amniotic Fluid.-Table I depicts an analysis of the instances of meconium staining of amniotic fluid alone as a sign of fetal distress.

266 1'he

GINSBURG reeo~rnition

of thi!'l

!'li~rn

Am.]. Obst. & Gynec. Augu-;t, 195':""

iR fiPnPnrlrmt. nnon rnnt.m•P. of H1P. 11mninti,. mPm-

branes. ~The meconiu~n--;pp~a;~d -i~~~~di~t~l~- ~ft~~ -r~pt~-;e -i~---;l;~~o~t-~~ll cases. No difference was noted in the outcome whether it appeared at once or during subsequent hours. All the deli n·ries were vaginal except for one cesarean section for failed trial of labor. "While numerically meconium staining alone Jid not signify fetal jeopardy, this sign was not entirely benign be· cause 9 babies were affected at birth. There were 2 neonatal deaths: one within 2 days from multiple congenital anomalies incompatible with life, the other within 7 hours of birth due to respiratory failUl'e. In the latter case, it was noted that the fetal heart souncls had been recorded at infrequent intervals during labor with no notation for 40 minutes prior to Jelivery. It is possible that significant fetal heart rate ehangps hall ocemTPd without having lwcn noted. 'l'ABLE I.

MECONIUM STAINING ALONE IN VERTEX PRESENTA'l'IONS

CONDITION OF NEWBORN NO. OF % OF NOT AF·I AF· I STILL· CASES SERIES FECTED FECTED BORN

77

50

68

------

9 -----

0

CONDITION OF NEWBORN IN 4 DAYS I I

GOOD

74

I

POOR

1

I NEO· NATAL DEATH

FACTORS ACCOUNTING FOR THE SIGNS TOTAl. I I MOR· ANATOM·I r>Y· TALITY ICAL NA:I.UC NONE ]0 21 46 2

Factors to account for the meconium staining were present in 31 cases. The anatomical factors consisted of 18 cord accidents, 2 placental accidents, and 1 congenital anomaly. The dynamic factors were 7 long or precipitate labors, 2 instances of Pitocin spasm, and one of maternal anoxia due to prolonged laryngospasm. Even though most of the infants were not severely affected, the proportion of potentially dangerous factors was considerable. Meconium staining in vertex presentations means that the fetus is in distress at least transiently, and that the factors responsible for this occurrence may persist, or they may recur with increasing severity. 1'herefore, meconium staining alone should serve as a warning of potential fetal jeopardy, and thereafter the patients should be observed continually for other signs of fetal distress. Fetal Bradycardia.-Table II depicts the cases with slowing of the fetal heart rate below 100 beats per minute. V1 orty-eight of the patients showed this sign, 15 with and 33 without meconium staining. Eight patients had the added sign of increased fetal heart rate eithPr before or after the onset of the slowing. In 21 cases, the fetal heart rate dropped only with contractions and recovered in the interval phase. In the remainder, the slowing was continual. 1'he fetal outcome was no worse in those cases in which the heart rate was continually slow. Ii1urthermore, slowing with contractions did not necessarily indicate a demonstrable cord accident or abnormality. Fourteen of the 48 babies with hr·adycardia were mnrkedly affceted at bitth, 2 were stillborn, and 2 died within 4 days. A greater proportion of affected babies and stillbirths was seen in the subgroup with the added factor of meconium staining . . A..lso, a greater proportion of babies in poor condition after 4 da:y·s and of neonatal deaths occurred in this group. Dynamic or anatomical causes for the potential fetal distress were found in 41 of the 48 cases. Anatomical causes were 16 cord accidents, 3 placental accidents, and one congenital anomaly. Dynamic factors were 8 cases of Pitocin spasm, 5 of cephalopelvic disproportion, 4 of long or precipitate labor, 2 of maternal hypotension, and 2 instances of pre-eclampsia. In this group,

267

SIGNIFICANCE OF SIGNS OF l<'ETAL DISTRESS

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3 cesarean sections were done, 2 for fetal distress and one for abruptio placentae. The remainder of the babies were delivered vaginally, 18 of whom showed sufficient distress to prompt immediate delivery. In the rapid delivc·ry group, 6 babies were affected at birth, 2 were stillborn, and 2 died within 4 days. The latter 4 deaths constituted the total mortality in the bradycardia group. Slowing of the fetal lwart rate below 100 beats per minute indicates highly significant fetal distress and the added presence of meconium staining is still more significant. There is some suggestion that prolonged continuous, or recurrent intermittent slowing of the fetal heart rate may indicate a graver fetal outcome, but proof of this must await the use of a method for thP eontinuous rC'eording of fetal heart tones. TABLE

II.

SLOWING OF FE1'AL liEAm' RATE

CONDITION OF NEWBORN

I

I

('0NTll1'1U:>I cw NEWBO!{N IN 4 DA 'iS

I

NO. OF %OF 1\0'l' AF· I AF- I STILLCASES SERIES F.ECTED FECTED ~~Il,]'< (JOOD

Slowmg alone 33 Slowing with meconium 15 Total 48

22

25

7

10 32

7 3''

14

I

1'0TAL MOR- ANATD:\1· I I NATAL KEOICAT. POOR DEATH 'l'ALTTY

1

31

0

2

11 42

2 2

7

FACTORS ACCOUN'I'Jr\(l ;'OR THE RIGNS

!]

DY-

I

:-!AMWI

N

13

17

:l

4 21

4

1

2

7

2

±

20

-·-·--·..

7 -~-~

Fetal Tachycard?:a.-Tablc III shows the cases with increase of the fetal heart rate above 170 beats per minute. Twenty patients presented this sign, !l with and 11 without meconium staining. The relationship to contractions did not appear to be important in the outcome. The fetal danger was far less significant than in the preceding group. There were no intrapartum or neonatal deaths. Five of the 20 infants were affected at birth, bnt only one was in poor condition after 4 days. TABLE 1

1

I

I

III.

RISING FETAL HEART RATE

cmmrr~o~~-?F NEW-

~'ECTED

!>VJ:<"

NO. OF %OF NOT AFAFSTILLCASESISERIES, IFECTEDI BORN

Rising alone 11 Rising with meconium staining 9 Total 20

?~.~~Mw-J I """'' I"''±:'""" I NEO-

J~'AC~~~~~~<;?T~~~INH

1 co.~r~:r;~~

GOOD

I

NATAL POOR I DEATH

TOTAL MOR'rALITY

I I

'V" '-="' """'"' ANA1'0MDYreAL I NAMICI

;o.;n:-.JI<:

!l

~

0

11

0

0

0

:l

1

7

6

6

0

8 19

1 1

0 0

0 0

2

15

3 5

0

13

2 3

12

7

5

5

The anatomical factors were 4 cord abnormalities and one placental accident. The dynamic factors were 2 cases of cephalopelvic disproportion and one of long labor. In this group, there was one eesarean section for placenta previa. The remainder of the infants were delivered per vaginam, 7 rapidly because of the constantly rising fetal heart rate. The fetal outcome was uneventful even when rapid vaginal delivery seemed to be indicated. Rising of the fetal heart rate above 170 beats per minute does not signify severe distress. The presence of meconium staining, however, as an additional sign, Jnay indicate some increase in fetal jeopard:r.

TABLE

IV.

'J.'ABLE

V.

RA'n: WITH MECONIUM STAINING

'l'U1'AL CASES OF FETAL DISTRESS

FLUCTUATION OF FETAL HEART

l'-'

.....

> 3

::;2

::c

'::::!

::0

z:c

c;::

O'l 00

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SIGNIFICANCE OF SIGNS OF FETAL DISTRESS

269

Fluctuation in the Fetal H cart Rat e.-Table IV shows a few instances of fluctuation in the fetal heart rate of 40 or more beats per minute with meconium staining. The fetal outcome was entirely uneventful in this group. Definite factors were present to account for the signs in most instances, howevrr. All of the patients were delivered vaginally in a normal way. Fluctuation of the rate within the limits of 100 to 170 beats per minute does not appear to indicate significant distress. Stmmtary of Results.-The entire series is summarized in Table V. Of 152 patients with signs of fetal distress, 1.3 per cent of the babies were stillborn, 2.6 per cent died in the neonatal period, 18.4 per cent were affected at birth, and 2.6 prr crnt wrre in poor condition after 4 days. Comment A comparison of the Service infant wastage during this study period with that of this particular series is interesting. The incidence of intrapartum deaths in all deliveries was 0.3 per cent in contra:st to the 1.3 per cent in this series. Following all the deliveries during the study period, the neonatal death rate was 1.2 per cent against the 2.6 per cent in this series. The total intrapartum and neonatal mortality for all deliveries was 1.3 per cent against 3.9 per cent in this series. These figures indicate the generally grave prognostic signifieance of the recognized signs of fetal distress. A more diligent search for the signs of fetal distress might have resulted in the salvage of 4 of the 6 infants who died in this series. In the entire study group, 55.9 per cent showed anatomical or dynamic causes for the fetal distress. They included cord accidents in 28 per cent, rapid or long labor and cephalopelvic disproportion in 12 per cent, Pitocin spasm in 7 per cent, and placental accidents in 5 per cent. Summary

l. The signs of fetal di:stress occurred in 11.2 per cent of 1,363 deliveries. 2. Following these signs the total intrapartum and neonatal mortality was over twice that of the general population. 3. The most common factors to account for the signs of fetal distress were: cord accidents, labor defects, crphalopelvic disproportion, Pitocin spasm, and placental accidents. 4. Age, parity, prematurity, and postmaturity were not important factors in predisposing to fetal distress. G. Meconium staining alone in vertex presentations indicates a generally favorable outcome, but it should warn one to be on the alert for the other signs of fetal distress. 6. Slovving of the fetal heart rate below 100 beats per n1inute indicates vrry significant fetal jeopardy. The presence of meconium staining as an additional factor indicates even more sevrre trouble. 7. An increased fetal heart rate above 170 beats per minute does not signify sPvere fetal distress, but the presence of meconium staining as an additional faetor may indicate some increase in fetal jeopardy.

GINSBURG

270

Am. ] . Obst. & Gynec. August,

10~7

8. Fluctuation of the rate by 40 beats per minute "\Vithin the lhnit of 100 to 170 with meconium staining does not appear to indicate fetal distresK 9. Prompt recognition of the signs of fetal distress and decisive intervention when necessary should prove fruitful in lowering hoth infant mortality and subsequent evidence of damage to the central nervous systPm. This is an area of obstetries in which much can be
References 1. 2. 3. 4. 5. 6. 7. S. fl.

10. 11. 12. 13. 14. 15. 16. 17. 18. Hl. 20.

21.

McCall, ,T. 0., and Fulsher, R. W.: AM. J. 0BST. & GYNEC. 65: 1006, 1953. Richardson, G. C.: AM. J. 0BST. & GYNEC. 32: 429, 1936. Lund, C. J.: AM .•T. OBST, & GYNEC. 40: 946, 1940. Hunt, A.M.: M. Olin. North Ameriea 23: 1061, 193\l. DeLee, J. B., and Greenhill, J. P.: Principles and Practice of ObstetricR, e