A study of variable decelerations in association with other heart rate patterns during monitored labor EMANUEL Minneapolis,
A review of 1 ,011 consecutive intrapartum heart rate tracings yielded 37.3% with some degree of variable deceleration pattern. No differences in Apgar score distribution were observed in the presence of uncomplicated variable deceleration pattern when compared to those tracings marked normal. However, the presence of variable decelerations.in association with other heart rate patterns resulted in lower mean Apgar scores at 1 and 5 minutes, which were significantly diierent from those of the fetal heart rate (FHR) normal group. Mean Apgar scores at 1 and 5 minutes were significantly different from normal when variable decelerations were noted in the presence of tachycardia and loss of variability. Mean Apgar scores were lower when bradycardia (prolonged episodes of heart rate Cl20 bpm) was present in the record when compared to normal, but the presence of variable decelerations with bradycardia did not result in different mean scores. The presence of baseline changes with loss of variability and variable decelerations appeared to result in the lowest mean scores. When bradycardii or tachycardia occurred in exclusive association with variable decelerations, the percentage of depressed newborn infants was relatively high. (AM. J. OBSTET. GYNECOL. 135:360, 1979.)
is a major problem in intrapartum biophysical monitoring. Mixed multiple heart rate patterns are common during intrapartum monitoring. While certain combinations are associated with fetal asphyxia, such as loss of baseline variability and tachycardia, little is known of the predictive value when several heart rate patterns are present simultaneously in the record. Beard and associates’ reported increased morbidity when variable deceleration fetal heart rate (FHR) pattern was associated with loss of baseline variability and baseline changes, such as tachycardia or bradycardia. Cibils’ noted fixed baseline with loss of variability and tachycardia and the changing from one pattern to another in more than 50% of stressed infants. It is known that variable decelerations may reflect umbilical cord compression and are, if severe, associated with asphyxia on the basis of decreased placental perfusion. Shelley and Tipton reported a direct relationship between the area of FHR decelerations and DATA
From the Department of Obstetrics Hennepin County Medical Center, Minnesota Medical School. Received for @b&cation Accepted December
and Gynecology, and the University
June 6, 1978.
Reprint requests: Emanuel P. Gariarw, M.D., Department of Obstetrics and Gynecology, Hennepin County Medical Center, 701 Park Ave., Minneapolis, Minnesota 55415.
adverse newborn outcome. Recent reports indicate that heart rate patterns similar to a severe variable deceleration pattern may precede intraparum fetal death.4 These observations support the need to further define the significance of the variable deceleration FHR pattern, particularly in relationship to other patterns. The purpose of this communication is to relate observations on variable decelerations in combination with other patterns in a large series of monitored patients.
Materials A total of 1,011 consecutive intrapartum FHR records was available for analysis. All patients were on the Obstetric Service at Hennepin County Medical Center, Minneapolis. Fetal monitoring was performed with the Corometrics FMS 101 and 1OlA or the Roache Fetasonde. FHR was recorded with the use of spiral electrode, ultrasonic probe, or abdominal ECG, depending upon clinical circumstance. Gestational age was 36 weeks or greater in 975 patients and less than 36 weeks in 36 patients. Following completion of monitoring, records were reviewed by one experienced reader; FHR observations, as well as mode of delivery, birth weight, Apgar scores, and various other clinical data were recorded. Predominant heart rate patterns were interpreted according to criteria proposed by Hon.5 Multiple variables were, therefore, available for analysis. Following recording of heart rate observations, the 0002-9378/79/190360+04$00.40/0@
Table I. T tests comparing Apgar scores at 1 and 5 minutes patterns with those of women showing normal tracings Apgar FHR
Normal Variable deceleration Tachycardia Variable decelerations and tachycardia Bradycardia Variable deceleration and bradycardia Loss of variability Variable deceleration, tachycardia and loss of variability Variable deceleration, bradycardia and loss of variabilitv *When
I min. score
T value *
3!% 375 100 45
7.75 7.25 7.29 7.18
1.50 2.05 1.94 2.15
3.85 2.21 1.73
5 min scow
T value *
8.84 8.49 8.45 8.24
1.22 1.51 1.50 1.74
3.3 2.41 2.25
402 376 100 45
patient’s history sheets were reviewed for completeness and accuracy. After coding, computer analysis with cross tabulation of certain FHR variables was performed. MSUltS
The presence of variable decelerations during monitored labor was high, with 37.3% having some degree of this pattern. Table I indicates the distribution of multiple heart rate patterns, with corresponding mean Apgar scores at 1 and 5 minutes. In thisgrouping, the combinations do not exclude the presence of other patterns. Mean Apgar scores at 1 and 5 minutes for variable decelerations and for fetal tachycardia (extended episodes of’ heart rate > 160 bpm) were lower than the FHR normal group. However, further lowering of mean scores was observed when variable decelerations and fetal tachycardia were present simultaneously in the record. Extended fetal bradycardia (heart rate < 120 bpm) was associated with relatively low mean Apgar scores at 1 and 5 minutes when compared to the FHR normal group. Loss of FHR variability was also associated with lower mean Apgar scores at 1 minute (6.82 compared to 7.75 for normal) and at 5 minutes (8.21 compared to 8.84 for normal). When variable decelerations were noted in association with baseline changes or loss of FHR variability, the lowest mean scores were noted. For those particular groupings, t tests between mean scores of the various patterns described above with the FHR normal group iridicate significant differences (Table I). The seemingly higher significance levels obtained by FHR patterns observed singly or with lower mean scores is a function of sample size. Fig. 1 demonstrates a case of neonatal depression
Table II. Relative frequency of variable decelerations in exclusive association with other FHR patterns NO. 152 Variable deceleration only Variable deceleration and loss of beat-to-beat 11 variability Variable deceleration and bradycardia 26 Variable deceleration, bradycardia and loss of. 3 beat-to-beat variability Variable deceleration and tachycardia 19 Variable deceleration, tachycardia and loss of 8 beat-to-beat variability 3 Variable deceleration, bradycardia and tachycardia 12 Variable deceleration and UPI
PO.cent 15.0 1.1 2.6
0.3 1.9 0.8
associated with loss of FHR variability, tachycardia, and decelerations. Variable decelerations with no other associated heart rate patterns were observed in 15% or 152 patients. The relative frequency of variable decelerations with other abnormal heart rate patterns, such as loss of beat-to-beat variability or tachycardia, and combinations of patterns is further illustrated in Table II. This group was relatively small, with only 0.3% to 2.6% of the study patients falling under this category. Table III reflects grouping by exclusive combinations. Women were grouped into low, medium, and high Apgar categories. Women with uncomplicated variable deceleration pattern (variable decelerations without any other associated abnormality) were compared separately with the distribution of the same Apgar categories for those whose FHR tracings were normal. Chi-square (x2) tests of significance are shown in Table
Fig. 1. Variable type deceleration pattern, tachycardia, after end of record kesulted in an asphyxiated neonate.
III. Relationship score. Chi-square
between variable deceleration pattern comparisons of variable deceleration Apgar
and loss of FHR
in exclusive association groupings with normal
1 min. score
with baseline values
5 min. SCOM
Chi square *
Normal: No. 5%
Uncomplic&ed variable deceleration (N = 151): NO. % Bradycardia and variable deceleralion (N = 26): NO. 70 Tachycardiu and variable deceleration (N = 19): NO. % *With
III. When FHR was recorded as normal, 96.7% scored a 1 minute Apgar of 4 or greater, while 98.6% scored 4 or greater at 5 minutes. Uncomplicated variable deceleration pattern was not differerit from the normal FHR group in their relationship to Apgar scores at 1 and 5 minutes. When bradycardia and variable decelerations occurred alone (without any other predominant pattern present), Apgar was significantly lower at both I and 5 minutes when compared to normal. When both bradycardia and variable decelerations occurred exclusively, 18.4% and 7.7% of neonates had Apgars of
less than 4 at 1 and 5 minutes. Although numbers are small, a similar trend is noted in the exclusive association of tachycardia and variable decelerations. When both were present exclusively in the record, the Apgar scores appear to be lower than the scores of the normal group at 5 minutes, but not at 1 minute. Table IV illustrates the relationship of variable decelerations and late decelerations occurring exclusively when compared to Apgar score with x2 comparisons of the late deceleration groups with noimal. The relationship between late decelerations and Apgar is also shown. Both
Table IV. Kelationship between variable deceleration (UPI) and .4pgar score with chi-square comparisons
Normal FHR No.
patterns in exclusive association with late deceler,itions of UPI groupings with normal values
(:hi squnrr *
(.V = 341):
% UPI and vatiabk dwrkration (IV = No.
%a UPI alow NO.
i!V = 26):
*With 2 degrees of freedom. groupings were associated with poor outcome and show a markedly lower Apgar distribution compared to the FHR normal group. However, with present numbers, it is difficult to determine whether the presence of variable decelerations with late decelerations is additive. The present data do not allow further breakdown as to severity of variable decelerations or to the various characteristics in terms of duration and severity of tachycardia and bradycardia. Such quantitive studies with regard to second-stage tracings are currently in progress.
Comment The variable deceleration pattern is generally thought to reflect umbilical cord compression mediated by reflex parasympathetic activity. However, a variety of circumstances may be associated with variable deceleration patterns, such as alterations in fetal PO, or blood pressure and maternal aorto-caval obstruction6, i These diverse mechanisms may help to explain
conflict in data interpretation. It may be that changes in fetal baseline heart rate or loss of variability, in the presence of umbilical cord compression, are reHections of further homeostatic adjustments reflecting the stress of decreased placental perfusion. It is of interest that the presence of uncomplicated variable deceleration patterns per se did not result in significantly different distribution in Apgar score when compared to the FHR normal group. Variable decelerations and tachycardia or bradycardia occurring together may be of greater significance. Further study is necessary to quantify these possible relationships. However, the presence of variable decelerations with baseline changes or loss of variability may be an indicator for further fetal assessment. I thank Thomas Allen of the University of Minnesota Computer Center for his statistical assistance and Dr. Donald W. Freeman for his critical review of the paper.
1. Beard, R. W., Filshie, G. M., Knight, C. A., and Roberts, G. M.: The significance of the changes in the continuous FHR in the first stage of labor, J. Obstet. Gynaecol. Br. Commonw. 78:865, 1971. 2. Cibils, L. A.: Clinical significance of FHR patterns during labor. Il. Late deceleration, AM. J. OBSTET. GYNECOL. 123:473, 1975. 3. Shelley, T., and Tipton, R. H.: Dip area. A quantitive measure of fetal heart rate patterns, J. Obstet. Gynaecol. Br. Commonw. 78:694, 1971.
4. Gaziano, E. P., and Freeman, D. W.: Analysis of heart rate patterns preceding fetal death, Obstet. Gynt=col. 50:578. 1977. 5. Hon. E. H.: An Atlas of Fetal Heart Rate Patterns. New Haven, Conn., 1968, Harty Press. 6. Ott, W. J.: The current status of intrapartum fetal monitor-ing, Obstet. Gynecol. Surv. 31:339, 1976. 7. Goodlin, R. C., and Lowe, E. W.: A functional umbilical cord occlusion heart rate pattern, Obstet. Gynecol. 43:22. 1974.