- Email: [email protected]
Fetal heart rate acceleration in labor: Excellent prognostic indicator
Fetal heart rate acceleration in labor: Excellent prognostic indicator 0.
HENDERSON
ARLENE JARLATH h’wfolk,
POWELL,
MEL\rlLLE.
M.D.
R.N.
MAcKEXNA,
M.D.,
F.A.C.O.G.
C’ir@nin
This study explores the significance of fetal heart rate acceleration in labor. Fetal heart rate accelerations were studied in 1,677 monitored laboring patients. Fetal outcome was analyzed according to perinatal mortality rate, Apgar scores, and incidence of late deceleration. The presence of accelerations of the fetal heart rate during labor proved to be an excellent indicator of subsequent good fetal outcome. (AM. J. OBSTET. GYNECOL. 134:36, 1979.1
the early sixties the role of electronic monitoring in the management of labor has assumed increasing importance. The initial three basic patterns described by Caldeyro-Barcia and colleagues’ and Hon2 have been refined so that now a great number of patterns can be identified and closelv associated with variants in fetal condition. In this study an extension of the work of. Rochard in France and Schifrin in this country” was carried from the antepartum period into labor. The) have originally described the usefulness of antepartum nonstress testing with good subsequent fetal outcome. In this study we have attempted to correlate fetal heart rate acceleration in labor with a similar prognosis. SINCE
Materials and methods During the 12 months from January 1, 1976. to December 31, 1976, 2,265 infants were delivered at DePaul Hospital, which is one of the teaching hospitals of the Eastern Virginia Medical School. Of these patients, 1,677 (74 per cent) were monitored electronically h? means of standard Corometrics 111B monitors.* Internal monitoring by means of a scalp electrode
was utilized in 1,276 patients. Intrauterine catheter was used in 848 patients. The remainder were monitored externally with Taco transducers and external ultrasound technique. Since the staff and residents have an agreed policy ot total monitoring, the only reasons for not monitoring patients were precipitous labor, lack of availability of a monitor. or elective cesarean section. The patients were drahvn from both the private and clinic segments of the obstetric population in the ratio of 65 per cent private to 35 per cetlt clinic (1 \CiiS. therefore, felt that this represented a cross-section of an average obstetric population. Classification of recognized fetal heart rate aud uterine contractility changes follow the standal-d classification of Hon.’ An acceleration was defined as an increase of fetal heart rate of 15 beats per minute above the normal baseline occurring with a contraction. Three accelerations occurring in a 15 minute period were necessary for inclusion in the acceleration category, Only uniform fetal heart rate acceleration patterns are included. Those accelerations occurring in association with decelerations or representing rebound phenomena were excluded lrom this stud!.
Results From the Diviwm I’irginiu Medical Rrceived,for Revised Jurle j4cceptedJune
of Perimztal Medicine, Eastern School, and DePaul Hospital.
publication
March
29, 1978.
12, 1978. 22. 197X.
Reprint requests: Dr. Jarlath MacKenna, Obstetrics and Gpecology, East Carolina Greenville, North Carolina 27834. *Corometncs Connecticut.
36
Medical
Department Universitv.
Systems, Inc., Wallingsfbrd,
of
The results of this study are detailed in I‘able I. l‘he perinatal mortality rate for all patients delivered at DePaul Hospital in 1976 was 18.6 per thousand. The perinatal mortality rate for that group of monitored patients was 14.9 per thousand. Fetal heart rate accelerations were present in 953 of those patients monitored (56.8 per cent) while no accelerations were ohserved in 724 patients (43.2 per cent). It is important to note the marked decrease in the puinatal rrxxtalicy 0002-9378/79/090036+03$00.3010
Cl lY7!l l-be (: V. tdosbv (2~
Volume 134 Number
FHR acceleration in labor
1
Table I. Perinatal Category
37
data
I
Number percentage
I
Late decelerations
I
5 Minute Apgar < 7
I
Perinatal mortality rate
Total deliveries
2,265/100%
-
5712.5%
18.6/1,000
Monitored
1.677174%
8715.2%
3412.0%
(42 deaths) 14.9/l .ooo (24 deaths) 27.2/1,000
Nonmonitored
588126%
-
2313.9%
Accelerations present Accelerations absent
953156.8%
11/1.15%*
8/0.84%*
724143.2%
76/10.49%*
76110.49%*
(18 deaths) 4.211 ,OOO* (4 deaths) 27.5/1,000* (20 deaths)
*P < 0.01. rate of those patients who exhibited fetal heart rate accelerations in labor. Only four patients showing this fetal heart rate change died, giving this group of patients the the excellent perinatal mortality rate of 4.2 per thousand. These four deaths were due to beta streptococcus pneumonia in a term infant, intracranial hemorrhage in a 37 week gestation infant delivered by midforceps, and respiratory distress syndrome in two preterm infants. The group of patients that did not show accelerations in labor had a much higher perinatal mortality rate of 27.5 per thousand, 20 deaths having occurred in this group. In evaluating these 20, it was found that conditions often associated with hypoxia (i.e. diabetes, postmaturity, sepsis, pre-eclampsia) were readily demonstrable in 16 patients. One may conjecture that the loss of accelerations in these infants can be related tcl the underlying pathophysiology of the fetal-placental unit, especially in cases where obvious causes of placental dysfunction can be demonstrated. Obvious explanations, however, are not available for all of these patients as two pre-term infants died of respiratory distress syndrome and two died from congenital anomalies. The improved outcome of neonates who showed intrapartum fetal heart rate accelerations is likewise demonstrated by observing the incidence of low Apgar scores and late decelerations in the varied groups studied. Five-minute Apgar scores of less than 7 occurred in only eight patients (0.84 per cent) with acceleration patterns present, while 26 patients (3.9 per cent) without accelerations had 5 minute Apgar scores of less than 7. The difference in the occurrence of late decelerations between the two groups is likewise striking. Only 11 patients (1.15 per cent) with accelerations exhibited late decelerations while 76 patients (10.49 per cent) without accelerations had late decelerations (Table I). The significance of the values of each of these three subgroups was evaluated with a chi square technique,
and differences for all three groups were found to be significant to a probability factor of less than 0.01. While no differentiation was made between vertex and nonvertex presentations when statistics were computed, breech presentations were examined separately. Of the 91 breech presentation infants delivered in this series, 76 were monitored. Only two of these failed to show accelerations in labor. There was one death among the breech deliveries. It occurred secondary to severe hypoxia in a vaginal delivery. Interestingly, accelerations were not present during labor.
Comment Rochard and associates3 have shown that fetal heart rate accelerations in response to fetal movement in the nonlaboring patient correlate well with fetal well-being and that this correlation can be used as a basis for a useful antepartum test. This assumption is based on the fact that fetal heart rate accelerations in response to movement are indicative of an intact and well-oxygenated central nervous system and secondary appropriate cardiac response. The benign aspects of a reactive acceleration pattern have been amply demonstrated in every study in which this sign has been looked for. In analyzing baseline recordings of fetal heart rate and uterine activity, both Schifrinl and Trierweiler and colleagues” have shown that the presence of increased accelerations virtually precludes the development of late decelerations in the subsequent stress of induced contractions. While the absence of accelerations has been shown to carry a much more ominous’prognosis. it is not as accurate a predictor of poor outcome as accelerations with movement are of good outcome.fi It would appear that our data substantiate the premise that a fetus with an intact neurocardiac system as demonstrated by accelerations in labor has sufficient reserve in terms of levels of oxygenation and placental reserve to well tolerate the rigors of labor. Our data suggest that, just as they do in
38
Powell,
Melville,
and MacKenna
the antepartum period, fetal heart ac.celerations lend reassurance in the intrapartum situation that the fetus who is healthy and shows the proper response to the stress of contractions, as demonstrated by acrelcrations, has an excellent likelihood of. tolerating labor and delivery without difficulty. While the absence of fetal heart rate accelerations is not as accurate a predictor 01 fetal distress, this lack of acceleration can, nonetheless. alert the obstetrician to be especially judicious in the
REFERENCES
I. Caldeyro-Barcia. R.. Mendez-Bauer, G., Poseiro, J. J., VI al.: Control of human fetal heart rate during labor. irt (:a~sels, D. E., editor: The Heart and Circulation in the New born and Infant: A Symposium, New York, 1966, Grunt 8~ Stratton, inc. 2. Hon, E. H.: An atlas ot’ fetal heart rate patlerns. New t-(:1ven, 1968, Harty Press. 3. Rochard, F., Schifrin, B. S., Goupil. F., et al.: Nonstressed fetal heart rate monitoring in the antepartum period, .4M. J. OBSTET. GYNECOL. 126: 699, 1976.
&. Schitrill, B. s.: Personal Lontnlulll(,atloll. i. ‘lrierweiler. ht. D.. Freeman. R. IL., md Jamrs, 1.: Baseline fetal heart rate characteristics as an indicator of’ fetal status during the antepartum period, AM. 1, OBYIW. (~YNEC!OL. ti.
125 (5): 61X. 1976. Foye, G.. Amato, J,, Vacknna,
published
J., and Sctlifrin,
tbdla.
Information for authors Most of the provisions of the Copyright Act of 1976 became effective on January 1, 1978. Therefore, all manuscripts must be accompanied by the following written statrment, signed by one author: “The undersigned author transfers all copyright ownership of the manuscript (title of article) to The C. V. Mosby Company in the event the work is published. The undersigned author warrants that the article is original. is not under consideration by another journal, and has not been previously published. I sign for and accept responsibility for releasing this material on behalf’ of any and all co-authors.” Authors will be consulted, when possible, regarding republication of their material.
B:
Un-
HENDERSON
ARLENE JARLATH h’wfolk,
POWELL,
MEL\rlLLE.
M.D.
R.N.
MAcKEXNA,
M.D.,
F.A.C.O.G.
C’ir@nin
This study explores the significance of fetal heart rate acceleration in labor. Fetal heart rate accelerations were studied in 1,677 monitored laboring patients. Fetal outcome was analyzed according to perinatal mortality rate, Apgar scores, and incidence of late deceleration. The presence of accelerations of the fetal heart rate during labor proved to be an excellent indicator of subsequent good fetal outcome. (AM. J. OBSTET. GYNECOL. 134:36, 1979.1
the early sixties the role of electronic monitoring in the management of labor has assumed increasing importance. The initial three basic patterns described by Caldeyro-Barcia and colleagues’ and Hon2 have been refined so that now a great number of patterns can be identified and closelv associated with variants in fetal condition. In this study an extension of the work of. Rochard in France and Schifrin in this country” was carried from the antepartum period into labor. The) have originally described the usefulness of antepartum nonstress testing with good subsequent fetal outcome. In this study we have attempted to correlate fetal heart rate acceleration in labor with a similar prognosis. SINCE
Materials and methods During the 12 months from January 1, 1976. to December 31, 1976, 2,265 infants were delivered at DePaul Hospital, which is one of the teaching hospitals of the Eastern Virginia Medical School. Of these patients, 1,677 (74 per cent) were monitored electronically h? means of standard Corometrics 111B monitors.* Internal monitoring by means of a scalp electrode
was utilized in 1,276 patients. Intrauterine catheter was used in 848 patients. The remainder were monitored externally with Taco transducers and external ultrasound technique. Since the staff and residents have an agreed policy ot total monitoring, the only reasons for not monitoring patients were precipitous labor, lack of availability of a monitor. or elective cesarean section. The patients were drahvn from both the private and clinic segments of the obstetric population in the ratio of 65 per cent private to 35 per cetlt clinic (1 \CiiS. therefore, felt that this represented a cross-section of an average obstetric population. Classification of recognized fetal heart rate aud uterine contractility changes follow the standal-d classification of Hon.’ An acceleration was defined as an increase of fetal heart rate of 15 beats per minute above the normal baseline occurring with a contraction. Three accelerations occurring in a 15 minute period were necessary for inclusion in the acceleration category, Only uniform fetal heart rate acceleration patterns are included. Those accelerations occurring in association with decelerations or representing rebound phenomena were excluded lrom this stud!.
Results From the Diviwm I’irginiu Medical Rrceived,for Revised Jurle j4cceptedJune
of Perimztal Medicine, Eastern School, and DePaul Hospital.
publication
March
29, 1978.
12, 1978. 22. 197X.
Reprint requests: Dr. Jarlath MacKenna, Obstetrics and Gpecology, East Carolina Greenville, North Carolina 27834. *Corometncs Connecticut.
36
Medical
Department Universitv.
Systems, Inc., Wallingsfbrd,
of
The results of this study are detailed in I‘able I. l‘he perinatal mortality rate for all patients delivered at DePaul Hospital in 1976 was 18.6 per thousand. The perinatal mortality rate for that group of monitored patients was 14.9 per thousand. Fetal heart rate accelerations were present in 953 of those patients monitored (56.8 per cent) while no accelerations were ohserved in 724 patients (43.2 per cent). It is important to note the marked decrease in the puinatal rrxxtalicy 0002-9378/79/090036+03$00.3010
Cl lY7!l l-be (: V. tdosbv (2~
Volume 134 Number
FHR acceleration in labor
1
Table I. Perinatal Category
37
data
I
Number percentage
I
Late decelerations
I
5 Minute Apgar < 7
I
Perinatal mortality rate
Total deliveries
2,265/100%
-
5712.5%
18.6/1,000
Monitored
1.677174%
8715.2%
3412.0%
(42 deaths) 14.9/l .ooo (24 deaths) 27.2/1,000
Nonmonitored
588126%
-
2313.9%
Accelerations present Accelerations absent
953156.8%
11/1.15%*
8/0.84%*
724143.2%
76/10.49%*
76110.49%*
(18 deaths) 4.211 ,OOO* (4 deaths) 27.5/1,000* (20 deaths)
*P < 0.01. rate of those patients who exhibited fetal heart rate accelerations in labor. Only four patients showing this fetal heart rate change died, giving this group of patients the the excellent perinatal mortality rate of 4.2 per thousand. These four deaths were due to beta streptococcus pneumonia in a term infant, intracranial hemorrhage in a 37 week gestation infant delivered by midforceps, and respiratory distress syndrome in two preterm infants. The group of patients that did not show accelerations in labor had a much higher perinatal mortality rate of 27.5 per thousand, 20 deaths having occurred in this group. In evaluating these 20, it was found that conditions often associated with hypoxia (i.e. diabetes, postmaturity, sepsis, pre-eclampsia) were readily demonstrable in 16 patients. One may conjecture that the loss of accelerations in these infants can be related tcl the underlying pathophysiology of the fetal-placental unit, especially in cases where obvious causes of placental dysfunction can be demonstrated. Obvious explanations, however, are not available for all of these patients as two pre-term infants died of respiratory distress syndrome and two died from congenital anomalies. The improved outcome of neonates who showed intrapartum fetal heart rate accelerations is likewise demonstrated by observing the incidence of low Apgar scores and late decelerations in the varied groups studied. Five-minute Apgar scores of less than 7 occurred in only eight patients (0.84 per cent) with acceleration patterns present, while 26 patients (3.9 per cent) without accelerations had 5 minute Apgar scores of less than 7. The difference in the occurrence of late decelerations between the two groups is likewise striking. Only 11 patients (1.15 per cent) with accelerations exhibited late decelerations while 76 patients (10.49 per cent) without accelerations had late decelerations (Table I). The significance of the values of each of these three subgroups was evaluated with a chi square technique,
and differences for all three groups were found to be significant to a probability factor of less than 0.01. While no differentiation was made between vertex and nonvertex presentations when statistics were computed, breech presentations were examined separately. Of the 91 breech presentation infants delivered in this series, 76 were monitored. Only two of these failed to show accelerations in labor. There was one death among the breech deliveries. It occurred secondary to severe hypoxia in a vaginal delivery. Interestingly, accelerations were not present during labor.
Comment Rochard and associates3 have shown that fetal heart rate accelerations in response to fetal movement in the nonlaboring patient correlate well with fetal well-being and that this correlation can be used as a basis for a useful antepartum test. This assumption is based on the fact that fetal heart rate accelerations in response to movement are indicative of an intact and well-oxygenated central nervous system and secondary appropriate cardiac response. The benign aspects of a reactive acceleration pattern have been amply demonstrated in every study in which this sign has been looked for. In analyzing baseline recordings of fetal heart rate and uterine activity, both Schifrinl and Trierweiler and colleagues” have shown that the presence of increased accelerations virtually precludes the development of late decelerations in the subsequent stress of induced contractions. While the absence of accelerations has been shown to carry a much more ominous’prognosis. it is not as accurate a predictor of poor outcome as accelerations with movement are of good outcome.fi It would appear that our data substantiate the premise that a fetus with an intact neurocardiac system as demonstrated by accelerations in labor has sufficient reserve in terms of levels of oxygenation and placental reserve to well tolerate the rigors of labor. Our data suggest that, just as they do in
38
Powell,
Melville,
and MacKenna
the antepartum period, fetal heart ac.celerations lend reassurance in the intrapartum situation that the fetus who is healthy and shows the proper response to the stress of contractions, as demonstrated by acrelcrations, has an excellent likelihood of. tolerating labor and delivery without difficulty. While the absence of fetal heart rate accelerations is not as accurate a predictor 01 fetal distress, this lack of acceleration can, nonetheless. alert the obstetrician to be especially judicious in the
REFERENCES
I. Caldeyro-Barcia. R.. Mendez-Bauer, G., Poseiro, J. J., VI al.: Control of human fetal heart rate during labor. irt (:a~sels, D. E., editor: The Heart and Circulation in the New born and Infant: A Symposium, New York, 1966, Grunt 8~ Stratton, inc. 2. Hon, E. H.: An atlas ot’ fetal heart rate patlerns. New t-(:1ven, 1968, Harty Press. 3. Rochard, F., Schifrin, B. S., Goupil. F., et al.: Nonstressed fetal heart rate monitoring in the antepartum period, .4M. J. OBSTET. GYNECOL. 126: 699, 1976.
&. Schitrill, B. s.: Personal Lontnlulll(,atloll. i. ‘lrierweiler. ht. D.. Freeman. R. IL., md Jamrs, 1.: Baseline fetal heart rate characteristics as an indicator of’ fetal status during the antepartum period, AM. 1, OBYIW. (~YNEC!OL. ti.
125 (5): 61X. 1976. Foye, G.. Amato, J,, Vacknna,
published
J., and Sctlifrin,
tbdla.
Information for authors Most of the provisions of the Copyright Act of 1976 became effective on January 1, 1978. Therefore, all manuscripts must be accompanied by the following written statrment, signed by one author: “The undersigned author transfers all copyright ownership of the manuscript (title of article) to The C. V. Mosby Company in the event the work is published. The undersigned author warrants that the article is original. is not under consideration by another journal, and has not been previously published. I sign for and accept responsibility for releasing this material on behalf’ of any and all co-authors.” Authors will be consulted, when possible, regarding republication of their material.
B:
Un-