Nonstressed fetal heart rate monitoring in the antepartum period

FETUS, PLACENTA, AND NEWBORN

Nonstressed fetal heart rate monitoring in the antepartum period FRANCE

ROCHARD,

BARRY

S.

FRANCOISE HELENE

M.D

GOUPIL, LEGRAND,

JOSETTE

M.D. M.D.

BLOTTIERE,

CLAUDE Paris,

M.D

SCHIFRIN,

SUREAU.

FWWP,

M.D. M.D.

and Boston,

Massachusetts

The role of nonstressed monitoring of the fetal heart rate (HR) in determiningfetal icwll-being during the antepartum period was assessed in 125 high-risk patient.?. Observations on HR, variability, and HR response to fetal movement (FM) and uterine 6 b.p.m.. and accrleratioas with FM) appea.rs to be a reliabte indicator of fetal well-being. ,411 the 51 Jetuses exhibiting this pattern sun&ed. This group also had the lowest incidence of neonatal complications. On the other hand, of the ba,bies who failed to .show sariabilitv > 6 b.p.m. or accelerations with FM (nonreactive pattern), 40 per cent died in the perinatal period. Thirty-jive patients shozcied features qf both a reactive and nonreac.tive pattern (combined pattern). Poor outcome in this group ulas confined to th.o.w in whom the majority of the pattern uu nonreactive. An undulating HR pattern wiih virtually absent variabilitv (sinusoidal pattern) was found in 20 Rh-srnsitiwd f&w, 50 per cent of whom &ed in the perinatal period. Bradycardia and tachvcardia uwe not f)iund to be reliable signs of fetal distress arrtepartum. Of the 12 jiitus~s who died during obscrzmtion, six showed late decebrations urith spontaneous UC hut all showed diminished variabilitv. The close correlation between nonstressed patterns and neonatal outcom.e demonstrated by this preliminary study warrants further use of thi.s tethniqrte,fr,rfetnl ezlnluation. (AM. J. OBSTET. GYNECOL. 126: 699, 1976.)

From Clinique Baudelocqw, Universite Rem Descartes, Ob.rtetrics und Gynecology, I.srael Hospital, Boston. Received for Revised

publicatzon

Service of Professor LePage, Paris, and thp Department of Harvard Medical School, Beth

December

OBSTETRICIANS HAVE long searched for methods of antepartum fetal evaluation that would be noninvasive and accurate and yield results that were immediately available. Ideally. the test should also be repeatable md incur minimal expense and inconvenirnce. While many biochemical and biophysical measurements have been proposed for antepartum fetal evaluation, few of these measurements have reliably predicted fetal outcome and even fewer have been show1 to improve

IO, 1974.

Ma? 21, 1976.

Accep~edJune

17, 1976.

Reprint requests: Dr. Barn, S. Schifrin. Department of Obstetrics and Gynecolog?r, Cedars-Sinai Medical Center, 8700 Brverl~ Blvd., L.os Angeles, California 90048.

699

Table

I. Antepartum

monitoring

pattern

Pattern Reactive

classification No.

51

Stable heart rate (120-160 b.p.m.) Variability > 6 b.p.m. Acceleration with fetal movement Nonreohz~e

19

Stable heart rate (120-160 b.p.m.) Variability < 6 b.p.m. No accelerations with fetal movement Sinusoidal

20

Stable heart rate (120-160 b.p.m.) Variability < 2 b.p.m. Sinusoidal pattern Frequency 2-5 per minute Amplitude 5-10 b.p.m. Combinrd

35

perinatal outcome when they were tested in a controlled setting. Others as well as our group have shown a close correlation between fetal heart rate patterns during labor and neonatal outcome.” * Both this correlation and the availability of techniques for electronic monitoring of fetal heart rate and uterine activity from the maternal abdominal wall have prompted the application of this surveillance technique to the antepartum period. One approach has resulted in the development of the contraction stress test or oxytocin challenge test. Here, the heart rate pattern in response to induced or spontaneous uterine contractions has been shown to reliably predict fetal well-being.3’ ’ In this study, we have adopted an approach first promulgated by Hammacher’ and then by Kubli and associates’ involving nonstressed monitoring of the fetal heart rate and uterine activity in the antepartum period. We present here our encouraging experience with this surveillance technique.

Material and methods Population. Patients were drawn from both private and clinic populations of the Clinique Baudelocque in Paris, France. This facility is a referral center for Rh-isoimmunization problems in pregnancy which explains the large number of such patients in the study. Patients classified as having “threatened premature labor” were those admitted in labor before 37 weeks. In 15 of these, contractions ceased spontaneously. The remaining eight patients received uterine relaxants to inhibit contractions. Only two of the 23 patients progressed to delivery. Patients classified as having “suspect postmaturity” had gestations of greater than 42 weeks by conventional clinical criteria. The designation “premium baby” was applied in a group of women in

whom social or demographic factors suggested itrcreased risk of poor outcome, for example, the eltlerl~~ primigravida. In the latter three groups, there vvere no obvious obstetric or medical problems. The rniscellaneous group included three patients with prev-ioils fetal loss and one each with hyperemesis, kidnrv stones, anemia, hydramnios, jaundice of yregnancv, and mitral insufficiencv. Because one of our goals was to determine the relationship between nonstressed heart rate patterns and neonatal outcome, it was important that intervention not be influenced by test results. Thus, in the beginning of the study, the results were not made available to the physicians managing the patient. J’atient management was based on clinical data and laboratory tests. including 24 hour urinary estriol determinations and biochemical analysis of anniotic fluid where indicated. As the study progressed, it was 111) longer possible to prevent intervention on the basis of these patterns. Ideally, intervention studies should be considered only if it can be shown that nonstressctl heart rate patterns predict fetal outcome. Technique. Heart rate and uterine activity patterns were obtained with a microphone transducer and a tocodynamometer combined in the Hewlett-Packard cardiotocograph.* Patients were maintained in the semi-Fowler position on a comfortable bed. Fetal movement was detected as a transient rise on the uterine contraction channel and confirmed by palpation or questioning of the patient. Recordings were continued for at least 30 minutes. This minimal time was chosen because of data suggesting that fetuses undergo sleep-wake cycles about 20 minutes in length.’ Recording for 30 minutes would hopefully assure us of at least a brief period of festal wakefulness. Classification of heart rate patterns. Records were analyzed for base-line heart rate, variability, and the heart rate response to spontaneous contractions and fetal movements (Table I). Heart rate patterns were classified as reactive, nonreactive, sinusoidal, and combined. A “reactive” heart rate pattern demonstrated a stable base-line rate usually between 120 and 160 beats per minute. The range of base-line variability was six beats per minute or greater, and accelerations accompanied fetal movement (Fig. 1). “Nonreactive” patterns were characterized by a stable base-line heart ratt usually between 120 and 160 beats per minute (Fig. 2). However, the variability was consistently less than six beats per minute. and there were no accelerations with fetal movement. Patterns were characterized as *Hewlett-Packard

Co., Waltham. Massachusetts

Nonstressed

Fig. 1. Reactive

heart rate pattern. The heart rate is stable 10 beats per minute, and accelerations accompany

is about

Fig. 2. Nonreactive Variability

“sinusoidal”

when

is less than

periodic

this

oscillations

in the heart

rate

superimposed

report,

prolonged

neonatal

tnmtoring

701

Vxiahilir~

heart rate pattern. The heart rate is stable at about 130 beats per minurc two beats per minute. and accelerations do not accompany fetal movement.

on a nonreactive pattern (Fig. 3). The frequency of these fluctuations varied from two to five per minute, and the amplitude ranged from five to 10 beats per minute. “Combined” heart rate patterns revealed combinations of both reactive and nonreactive heart rate patterns (Fig. 4). Measures of outcome. The measures of outcome utilized in this report were: (1) fetal survival or death; (2) presence or absence of fetal distress during labor; and (3) prolonged neonatal hospitalization (at the Clinique Baudelocque, parturients are confined to the hospital tar six days after delivery; for the purpose of were

at about 130 beats per minute. fetal movement.

FHR

stay

denotes

hospitali-

Tation of the neonate beyond six days of life): (4) presence or absence of stigmas of intrauterine growth retardation (birth weight less than the tenth percentile for gestational age). respiratory distress syndrome, or fetal anemia (fetal cord hemoglobin less than 13 gm. per cent).

These measures of outcome ww ~e(l (0 test the null hypothesis that knowledge of’ nons~rwsed fetal heart rate patterns in the antepartum peri1x1 ~;ulnot he used to predict fetal outqme.

Results A total of 641 recordings were ohtaiwd li)r these 125 patients. The earliest gestation ;II ~~.hich monitor-ing was performed was 25 weeks, and the larest \vas 44 weeks.

‘The

greatest

number

of tests

in otlc’ patient

was

30 and the least number was one; the aver;tge was five. The indication for nonstressed rnonicoring in 12.5 patients according to interpretation of’ the nonstressed pattern

according III.

Of

is indicated

in Table

11. The

to heart. rate pattern the 5 1 babies

with

lwrilxital

outcomr

is presented

persistently

~-eat-tiw

in Table patterns,

41 (80 per cent) tolerated labor without distress. were delivered in good condition, and had a normal followup. Six babies (12 per cent) developed fetal distress during

labor,

and

ii)ur

were

affwtwl

\vith

intrauterine

702

Rochard et al.

Fig. 3. Sinusoidal heart rate pattern. The heart rate is stable at about 130 beats per minute. The short-term variability is less than two beats per minute. The amplitude of the sinusoid is about 10 beats per minute, and the frequency is two cycles per minute.

Fig. 4. Combined patterns.

heart

rate

pattern.

Pattern

growth retardation, the respiratory distress syndrome, or anemia. All of the infants with persistently reactive tests survived. Of the 19 fetuses demonstrating persistent nonreactive patterns, five (26 per cent) died in utero or in the neonatal period, eleven (58 per cent) required prolonged neonatal care, and only three of the 19 were mildly affected or had fetal distress from which they recovered during labor. None of these babies was unaffected. The majority of these babies were found to be severely affected as a result of maternal Rh isoimmunization. Four had the respiratory distress syndrome. Sinusoidal heart rate patterns were observed only in babies with severe isoimmunization. Of the 20 babies manifesting sinusoidal heart rate patterns, 10 (50 per cent) died either in utero or in the neonatal period, an

illustrates

features

of both

nonreactive

and

reactive

additional eight (40 per cent) required prolonged hospitalization. Eighteen of the 20 had moderate to severe hydrops. Only two of the 20 babies with sinusoidal patterns survived without benefit of prolonged neonatal care. Combined patterns were found in 35 patients. To assist

in

the

evaluation

of

combined

patterns,

the

duration of each component in each 30 minute record was calculated and compared to the outcome. For the 17 babies with a poor outcome, the mean percentage of nonreactive pattern was 55 per cent. For the 18 babies who did well at birth, nonreactive patterns accounted for 31 per cent of the recording time, on the average. To further facilitate analysis of combined patterns, we arbitrarily divided these records according to the predominant pattern. Nine of 10 fetuses (90 per cent) demonstrating nonreactive heart rate patterns for

Nonstressed

Table

II. Antepartum

Patent

patterns

III. Perinatal

labor

outcome

according

Rf?a&W

Cnmbked

iv#nrPfutiw

6 18

10 5

i-1 -

10

8

5 4 8 51

5 2 25 35

to nonstressed

Reactive

Good outcome Mildly affected Prolonged neonatal Caere Fetal death Neonaml death ToGli

41 6 4 0 0 51

Table IV. Perinatal outcome predominant pattern

according

Perinatal Pwdominant pa&r?2

Good

Reactive and

68

?50%

~50%

Reaxtiw

16 5 4 0 0

outcome

Prolonged

care

Death

Total

8

0

76

IO

23

16

49

78

31

16

125

reactive

Nonreactive, sinusoidal. and ~50% react& Total

703

more than 50 per cent of the recording (~50 per cent reactive) died in utero or required prolonged hospitalization. On the other hand, 80 per cent of babies in whom the predominant pattern was reactive (250 per cent reactive) did well. When the various categories were combined into the reactive group (reactive and ~50 per cent reactive) and the nonreactive group (nonreactive, sinusoidal, and <50 per cent reactive), an even more striking correlation with outcome was shown (Table IV). During the studs, no fetus went from a reactive to a persist.enrly nonreactive pattern. On six occasions, patterns were interpreted as nonreactive for the period of observation but became reactive with further testing or subsequent tests. These patients were listed in the reactive group. Little c orrelation could be demonstrated between

Total

50 2.‘3 20

-. -

I 2 19

20

10 7 13 12.3

heart rate pattern heaT-t rute pattern

<50% Reactiw

io

to

20

2

1 4 4 I 0

25

SiW.SOidfd

-

No&ressed OUtCOVlP

momtoring

.--

popdafion

Rh isoimmunizaCon Threatened premature Toxemia Diabetes Suspect postmaturity Miscellaneous Total

Table

FHR

Nonrmctiw

0 3 11 4 1 19

base-line fetal heart rate or variability and weeks of gestation. Also we did not find any strong predictive correlation between base-line tachycardia or bradvcardia and outcome (Table V). Of the six babies with base-line rates 2160 beats per minute. three did well, one died in utero, and three developed fetal distress during labor. The four babies with heart rates consistently below 120 beats per minute did well. Spontaneous decelerations (usually variable decelerations) without contractions were found in 13 patients. Uterine contractions were present in 6 1 per cent of the tracings, the frequency increasing with advancing gestational age. Of the 77 patients exhibiting uterine activity, fetal decelerations were found in 23. While decelerations with contractions, especially late decelerations. were found more frequently in severely affected babies, the presence or absence of decelerations did not improve the predictive accuracy of the underlying heart rate pattern (Table VI). Late decelerations with spontaneous contractions were found onlv with nonreactive heart rate patterns. During the period of study. 12 fetuses died under observation. While the mean heart. rate in this group of babies was higher than in survivors, nom* demonstrated frank bradycardia, and only one showed tachvcardia. Contractions were present in each case, but only seven of 12 demonstrated late decelerations. Without exception. however. there was a progressive diminution in beat-to-beat variability in I~C base-line heart rate as death approached.

704

Rochard

Table

V.

between

et al.

Antepartum monitoring: Relationship base-line rate and outcome

Tochyrardia

(>160

b.p.m.)

6

Good outcome Intrauterine dead) Fetal distress during labor Brad~~mdio

(
Table

VI.

Outcome of periodic

Pattern

Reactive

Combined

RwordA with periodic decelerations

4 Good outcome-3 14 Severely affected-14 (43%) PerinaraI death-6 5 Good outcome-3 (60%‘)

3 I

affected

according to pattern deceleration

(75%)

Nonreactive

1 2 4

b.p.m.j

C$od outcome Rh isoimmunizaGon-mildly

presence

3

and

Reconi5 without periodic o!melerations 24

Good outcome-18 (75%) 15 Severely

affected-14 (42%) PerinataI deaths-5 15 Good outcome-8 (47%)

Eight infants (10.5 per cent) of the 76 patients of the predominantly reactive group were premature by birth (birth weight less than 2,500 grams). Three of these developed the respiratory distress syndrome but survived. Of the 36 babies of the predominantly nonreactive group who were born alive, six (16.6 per cent) were premature by birth weight. Three of these developed the respiratory distress syndrome, and two died.

Comment The results suggest that reactive heart rate patterns in the antepartum period indeed reflect fetal wellbeing. Of the 76 high-risk fetuses in whom the predominant heart rate pattern was reactive (reactive and ~50 per cent reactive), only 8 (10.5 per cent) required prolonged neonatal stay and all survived. Of the 49 fetuses with predominantly nonreactive patterns (nonreactive, sinusoidal, and ~50 per cent reactive), 23 (47 per cent) required prolonged neonatal care and 20 more (41 per cent) died either in utero or in the neonatal period. All of the babies who died in utero demonstrated progressive loss of variability: none had reactive patterns. The benignity of the reactive pattern is supported by data from base-line recordings of heart rate and uterine activity preceding contraction stress testing.’ Schifrin and colIcagues’, ” reported that when accelera-

tions with good variability were present no fktus dewIoped late decelerations during the stress of induced contractions. Lee and co-workers’ have also co~~ludd that accelerations with fetal movement are a reliable sign of fetal well-being. Kubli and associates’ and Hammache?’ have made similar claims for “good variability” without specifying accelerations with fetal movement. The testing procedure proposed here is perhaps the simplest form of antepartum heart rate evaluation. A microphone and a tocodynamometer are applied to the maternal abdominal wall, and observations on heart rate, uterine activity, and fetal movement arc carried out. The results are immediately available, and the test can be repeated frequently or continued indefinitely. Neither stress nor stimulus is provided in this test. It is believed that both normal and pathologir fetuses produce characteristic heart rate patterns, but there is no clear-cut separation of respiratory and nutrit& function of the placenta as has been proposed for the contraction stress test.’ Monitoring the fetus in this wal seeks to uncover the presence or absence of an adequate central nervous system inHuence on the heart rate pattern. As gestation advances, the fetal heart rate decreases and variability increases.’ This likely represents an increasing influence of the fetal central nervous system, especially the vagus, on the heart rate.’ Near term the normal fetus characteristically shows good variability (>I0 and ~25 beats per minute), a stable heart rate (between 120 and 150 beats per minute), and accelerations with fetal movement (reactive pattern). A useful feature of antepartum testing is the f&l heart rate response to spontaneous contractions. The frequency of contractions increases with advancing gestation. Ruttgers and colleagues’ have found that the frequency of contractions is less than three in 10 minutes until 36 to 37 weeks of pregnancy but increases progressively thereafter. At the thirtyeighth week, 80 per cent of the patients tested demonstrated spontaneous uterine activity. Mild variable-type decelerations with or without accompanying uterine contractions occur in about IO pel cent of normal fetuses; late decelerations in response to contractions generally do not occur. In the normal fetus there may be periods of decreased variabilit! which usually last less than 30 minutes. It is believed that these episodes represent fetal sleep-wake or restactivity cycles and do not signify fetal compromise. Compromised fetuses show persistently decreased variability, absence of accelerations with movement (nonreactive pattern), and late or undefined decelerations with contractions. Resting heart rates in these

Nonstressed FHR monitoring

fetuses are usually within the normal range. The loss of beat-to-beat variability appears to represent blunting of the homeostatic mechanisms for control of heart rate. There is an increased likelihood of late decelerations during spontaneous contractions in these fetuses. Z4n undulating heart rate with virtually absent beatto-beat variability (sinusoidal pattern) appears to be an ominous extention of the nonreactive pattern. The m%jority of babies with such patterns have died in utero or have been hopelessly compromised at birth.” This pattern likely represents a virtual absence of central nervous system control over the heart rate. SinusGdal patterns \t-ere found in nine of I2 fetuses prior to clcath in the series reported by Kubli and associates. Of the 20 fetuses demonstrating this pattern in this series, 50 per cent died in utero or in the neonatal period. and an additional 40 per cent required prolonged hospitalization after birth. Only 10 per cent of babies with a sinusoidal pattern had an uncomplicated course. Manseau and colleagues”’ as well as out- group have found sitlusoidal patterns in only those letuses severely affected with Rh isoimmunization. In the series reported by Kubli and associates” the sinusoidal pattern occurrecl in a more diverse group. Sinusoidal patterns found during labor have not been clearly related to asphyxia.” Repeated nonstressed testing in a group of fetuses who were to die in utero has provided insight into the sequence <)f changes tchich precede feta! death. In serial tracings prior to death, the most consistent feature has been a progressive loss of base-line beatto-beat variability in fetal heart rate patterns. No fetus with good variability died unexpectedly, Although base-Iin? tachvcardia has been observed more. frequently in babies who are about to die, in the majority, the base-line level5 are within the normal range. Base-

7OS

line tachycardia is neither a reliable nor ‘I constant sign of severe antepartum fetal hypoxia or impending fetal death. Persistent bradycardia has been the least con]manly observed of all the monitoring pamrns. It \\as observed in only one instance in a series of I2 antepartum deaths reported by K&Ii and assc)(,iates and in none of the cases reported here, It ma? bc, concluded that base-line bradycardia is not an carI\ sign of f&al hypoxia or impending fetal death Kubli and associates” found that the l~sence of’latc decelerations was a most consisten sign of’ severe f&al hypoxia and impending death. He fouml decelerations iu 91 per cent of the records with contractiorls in the premurbid group compared to only IO per cent of those in the control group. \Ve ha\‘{: also fcmnd a similar high incidence of decelerations iu the babies in the nonreactive group. The combinatiotl of’ a nonrtaac.tive pattern and late decelerations with spontaneous contractIons invariable presaged an ominot~s outco~~tc in thib studv. ‘IXese studies, in general, support the conclusions of Wtrtin and Lolleagues ” and Hobel and co-workers” who hale shown that ominous hear: rate patterns during labor are associated with an increased risk of death from respiratory distress in 11~ tleonatal period.“, ” While the incidence of. respil ator? distress in the predominantly reactive and pr~dominantlv nonreactive groups was similar, death occur1 cd only in the nonreactive group. However, the nurill~crs are quitv small. In summary. nonstressed surGllancc. of the fiatal heart rate in late pregnancy appears to provide reliable, predictive information about the fc*tal condition. The results of these studies warrant wide>pr(-*ad utilization of this test in controlled stud& to dt~terminc its effecr in improving perinatal outcome*.

REFERENCES

1.

Han% E. H.: Detection of fetal distress. Fifth World Congas of Gynaecology and Obstetrics, September, 1967. Svdnev. Australia, London 1967, Butterworth &

2. 3.

Schifrin, B., Dame, L.: J. A. M. A. 219: 1322, 1972. Schif’rin, B., Doctor, G., Lapidus, M,, et al.: Contraction stress test for antepartum fetal evaluation, Obstet. Cynecol. 45: 433, 1975.

co..

Ltci.

4. Lee, C. Y.. DeLoretas P. C.< and O’Lane, J. M.: A study of feral hea rye accelrration patterns. Obstet. Gynecol. 45: 142, 197-5, 5. Kubli, F. \V., Kaeset, L., and Hinselmann, M.: Diagnostic

management

of’chronic

placental insufficiency, in Pecile.

A., and Finzi, C., editors: The Foeto-placental Unit, Amsterdam, 1969, Exerpta Medica Foundation, pp. 323339. 6. Hammacher, K.: The clinical significance of cardiotocog-

raphy, vz Huntingford, P,, Huwr, M., and Saling. E., editors: Perinatal Medicine, New York. 1!170, Academic Press, pp. 80-93~ 7. Dreyfus-Brisac, C., and Blanc, (1.: Uectroencephalogramme et maturation cerebral!, Encvphale 45: 205, 1956. 8, Ruttgers, H.. Kubli, F., Ha&v-, o., Bacbmam~, M., and

Grunder,

E.: Die

antepartale

fe(aIe

Herzfrequen(

I. Verhalten van Gru~dfrequenz, Flulimation’ and Dezeierationen in Schwanzerschaft. 7. <;ehurLshilie Perinatol, 176: 294, 1972. -’ 9, Schifferli, P. Y., and Caldeyro-Barcia, R.: Effects of atropine and beta-adrenergic drugs on the heart rate of the human fetus, k/ Boreus, L., editor; Fetal Pharmacology New York, 1973, Raven Press. 10. Manseau, P., Vaquier, J., Chavinie, J.? and Sureau, cl.: Le rvthme cardiaque foetal sinusoidal. .4spwi evocateur de

:

706

Rochard et al.

souffrance foetale au tours de la grossesse, J. Gynecol. Obstet. Biol. Reprod. 1: 343, 1972. 11. Kubli, F., Ruttgers, H., Haller, U., Bogdan, C., and Ramzin, M.: Die antepartale fetale Herzfrequenz; Il. Verhalten von Grundfrequenz, Fhtktuation und Dezerationen bei antepartalem Fruchttod, Z. Gerburtshilfe Perinatol. 176: 309, 1972. 12, Schifrin, B, S.: Unpublished data.

13.

14.

Martin, C. B., Siassi, B., and Hon. E. H.: Fetal heart ran. patterns and neonatal death in low birthweight infants, Obstet. Gynecol. 44: 503, 1974. Hobel, C. J., Hyvarinen, M., and Oh, W.: Abnormal letal heart rate patterns and fetal acid-base balance in low birth weight infants in relation to respiratory distress syndrome. Obstet. GynecoI. 39: g3, 1972.