FETUS, PLACENTA, AND NEWBORN
Nonstressed fetal heart rate monitoring in the antepartum period FRANCE
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
Service of Professor LePage, Paris, and thp Department of Harvard Medical School, Beth
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
Ma? 21, 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.
Stable heart rate (120-160 b.p.m.) Variability > 6 b.p.m. Acceleration with fetal movement Nonreohz~e
Stable heart rate (120-160 b.p.m.) Variability < 6 b.p.m. No accelerations with fetal movement Sinusoidal
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
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
Fig. 1. Reactive
heart rate pattern. The heart rate is stable 10 beats per minute, and accelerations accompany
Fig. 2. Nonreactive Variability
is less than
in the heart
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.
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.
in otlc’ patient
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
to heart. rate pattern the 5 1 babies
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
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.
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
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
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
5 4 8 51
5 2 25 35
Good outcome Mildly affected Prolonged neonatal Caere Fetal death Neonaml death ToGli
41 6 4 0 0 51
Table IV. Perinatal outcome predominant pattern
Perinatal Pwdominant pa&r?2
16 5 4 0 0
Nonreactive, sinusoidal. and ~50% react& Total
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