AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 3
May 1991
SINUSOIDAL FETAL HEART RATE PATTERN DURING LABOR Charles C. Egley, M.D., Watson A. Bowes, Jr., M.D., and Denise Wagner, R.N.
ABSTRACT
The sinusoidal heart rate (SHR) pattern, when found during antepartum monitoring of the rhesus immunized pregnancy, is ominous.1-3 However, there is some question of the seriousness of the sinusoidal pattern when it is found during antepartum monitoring in the absence of rhesus isoimmunization.4-7 The meaning of the SHR pattern during labor is unclear. Six perinatal deaths have been reported to be associated with this pattern.4-5-8-10 However, when the SHR pattern during labor is examined in larger series,11-13 the neonatal outcome is nearly uniformly good. It is emphasized that the present report includes only cases of typical sinusoidal pattern (Fig. 1), defined as sine waves with a frequency of 2 to 5 per minute, an amplitude of 5 to 10 beats per minute (bpm), and short-term variability of less than 2 bpm. We examine the incidence of SHR pattern during labor, what drugs and maternal conditions influence the incidence of this pattern, the condition of the fetus who exhibits this pattern, and the relationship between the SHR pattern during labor and other fetal heart monitor patterns.
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Of 1280 consecutive fetuses monitored internally with a scalp electrode for at least 10 minutes during labor, 54 (4.2%) demonstrated the sinusoidal heart rate (SHR) pattern. Seven of these demonstrated the SHR pattern for more than 90 minutes. In six of these seven cases, the SHR pattern occurred during oxytocin administration. The SHR group did not differ from the 1226 fetuses not demonstrating the SHR pattern (NSHR group) in Apgar scores, incidence of other fetal heart rate abnormalities, or passage of meconium. The scalp pH was obtained from three fetuses in the SHR group and was above 7.30 in each. Alphaprodine administration during labor was associated with development of the SHR pattern, whereas other narcotic administration was not. The significance of "atypical" SHR pattern with increased amplitude is discussed, along with the need to adhere to strict definition of the SHR pattern.
MATERIALS AND METHODS
All fetal heart rate (FHR) tracings obtained with scalp electrodes (Corometrics spiral FECG electrode, Corometrics, Wallingford, CT) from fetuses of mothers laboring during a 6-month period between January 1, 1977, and June 30, 1977, were reviewed. Included in this study were only those fetuses of 30 weeks or greater gestation who were monitored with scalp electrodes for at least 10 minutes. In all, 1280 cases fit these criteria. The SHR is defined as typical sine waves with (1) a frequency of 2 to 5 per minute, (2) an amplitude of 5 to 10 bpm, and (3) short-term variability of less than 2 bpm (Fig. 1). Among the 1280 cases reviewed, 54 (4.2%) demonstrated the SHR pattern. These 54 cases (SHR group) were compared with the 1226 cases not demonstrating this pattern (NSHR group). Data were obtained from review of maternal and neonatal records. Chi-square analysis was used unless fewer than five cases were present in any one cell. In the event
St. Francis Medical Center, Peoria, Illinois and The Division of Maternal and Fetal Medicine, Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, North Carolina Reprint requests: Dr. Egley, University of North Carolina, Wake AHEC, 3000 New Bern Ave., Raleigh, NC 27610 Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
197
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 3 1
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Typical sinusoidal fetal heart rate pattern.
of fewer than five cases in any one cell, exact probability was calculated. The study period (1977) was used because we believe that little was known about the SHR during labor at that time. Thus, the presence of the SHR pattern should not have influenced patient management. Careful record review reflects this, in that there was no mention of the SHR pattern among the records of the 54 cases. RESULTS
SHR pattern occurred in a labor, it persisted for a mean of 47 minutes. This figure is skewed, however, by two cases in which the pattern persisted for more than 200 minutes. The seven cases in which the SHR pattern persisted for more than 90 minutes were analyzed separately. Among these seven cases there was no evidence of ABO or Rh isoimmunization or maternal complications (except for two mothers who gained more than 40 pounds during pregnancy). All seven cases had 1- and 5-minute Apgar scores greater than seven. Only one fetus passed meconium during labor. In six of the seven cases, however, it was found that oxytocin was used to augment or induce labor.
Incidence
The sinusoidal pattern was found in 54 (4.2%) of the 1280 cases studied. It was observed, however, that the SHR group was monitored with a scalp electrode for an average of 297 minutes compared with an average of only 180 minutes for the NSHR group. Therefore finding an SHR pattern may be a function of how long the fetus is monitored with a scalp electrode. Length of Time Sinusoidal
The length of time that the sinusoidal pattern persisted in a given labor varied from less than 1 minute to more than 4 hours (Table 1). When the
Length of Time Sinusoidal to Delivery
In only four cases did the sinusoidal pattern occur with 2 minutes of delivery. All four of these cases had 1- and 5-minute Apgar scores above seven and only one of the four had meconium passage at delivery. In six other cases the sinusoidal pattern was present within 10 minutes of delivery and in one other case the sinusoidal pattern was present within 15 minutes of delivery. In the other 43 cases the sinusoidal pattern had ended more than 15 minutes before delivery. Thus, Apgar scores may not reflect what the fetal condition had been during the time period the SHR pattern existed.
Fetal Scalp pH Table 1.
Length of Time the SHR Pattern Exists
Length of Time Sinusoidal (minutes)
198
Less than 10 10-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100 101-200 More than 200
No. Cases
12 9 5 4 6 3 1 6 1 2 3 2
Fetal scalp pH sampling was performed on three of the 54 cases during or within 5 minutes after an episode of SHR. The indication for the pH sampling was decreased short-term variability in all three cases and each time the pH was above 7.30.
Influence of Medications
The influence of medications commonly administered during labor was examined (Table 2). Although other medications (such as antibiotics, tranquilizers, prochlorperazine, magnesium sulfate, phenytoin) were administered during labor, the fre-
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May 1991
FETAL HEART RATE/Egley, Bowes, Wagner Table 2.
Influence of Drugs on the SHR Pattern SHR Group (n = 54)
NSHR Group (n = 7226)
Drug*
No.
%
No.
%
Significance
Alphaprodine Morphine sulphate Meperidine Methotrimeprazine/propiomazine All narcotics Meperidine/hydroxyzine Hydroxyzine Oxytocin
9 3 16 3 29 6 23 17
16.7 5.6 29.6 5.6 53.7 11.1 42.6 31.1
86 25 257 48 418 174 478 331
7.0 2.0 21.0 3.9 34.1 14.2 40.0 27.0
p =s0.01 p =0.09 NS NS p *SO.O1 NS NS NS
*Alone or in combination.
Meconium
Meconium was present either during labor or at delivery in 13 of 54 (24%) SHR cases and present in 257 of 1226 (21%) nonsinusoidal cases. There is not a statistically significant association. Other FHR Patterns
The SHR group did not differ statistically from the NSHR group in the incidence of variable decelerations, severe variable decelerations, accelerations, tachycardia, bradycardia, head compression patterns, or late decelerations (Table 3). Arrhythmias were suspected from the FHR tracing in 4% of the sinusoidal group and 3.9% of the NSHR group. Short-term variability was decreased or absent in all SHR cases during an episode of the SHR pattern. When decreased short-term variability was examined outside periods of sinusoidal pattern, it was found in 13% of SHR cases and in 14.7% of NSHR cases.
Table 3.
Other FHR Patterns
Maternal Condition Pattern
In none of the 54 cases with the SHR pattern did the mother exhibit hypertension, third trimester bleeding, significant proteinuria, diabetes, or less than 15 pound weight gain during pregnancy. Two of the 54 (3.7%) SHR mothers had heart disease, whereas 20 of the 1226 (1.6%) NSHR mothers had heart disease during pregnancy. Two of the 54 (3.7%) SHR mothers had anemia on admission, whereas 42 of the 1226 (3.4%) NSHR mothers were anemic.
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quency of administration was too low to generate meaningful statistics. Methotrimeprazine (Levoprome) and propiomazine (Largon) were always used as a combination in this study. In no instance was either drug administered alone. Meperidine (Demerol) and hydroxyzine (Vistaril) are examined as a combination because of the high frequency of administration of this combination in this series. The relationship between alphaprodine administration during labor and development of the SHR pattern is significant. Other narcotics did not significantly increase the occurrence of the SHR pattern. Furthermore, when the cases of SHR associated with morphine sulfate were analyzed, it was found that the morphine sulfate was administered after the SHR pattern had emerged in two. Thus, although there was an association between alphaprodine use and development of the SHR pattern, no such association was found with morphine sulfate, meperidine, or propiomazine. Hydroxyzine, either alone or in combination with other drugs, appears to have no influence on development of the SHR pattern. There appears to be no statistical association between oxytocin use and the SHR pattern, although six of the seven cases in which the SHR pattern persisted for more than 90 minutes were on oxytocin at the time the SHR pattern appeared.
Variable decelerations Accelerations Decreased short-term variability* Tachycardia 2=160 bpm Head compression Bradycardia ^ 1 2 0 bpm Late decelerations Severe variable decelerations Suspect arrhythmia =5 bpm lasting 5=10 minutes.
SHR Group (n = 54) (%)
NSHR Group (n = 1226) (%)
72.2 75.9 13.0 5.5 5.6 9.2 1.8 5.5 4.0
77.0 80.3 14.2 5.4 5.7 10.2 2.0 4.2 3.9
199
Apgar Scores
Table 5.
Depressed 1-minute Apgar scores (less than 7) were found in 3 of 54 (5.5%) sinusoidal cases and 64 of 1226 (5.2%) NSHR cases (Table 4). Depressed 5-minute Apgar scores were found in 1 of 54 (1.9%) SHR cases and 14 of 1,226 (1.1%) NSHR cases. Statistically, the difference is not significant at either 1 or 5 minutes. Gestation
Gestational assessment was made on each newborn. The SHR group did not differ significantly from the NSHR group in gestational distribution (Table 5). Anemia and Hyperbilirubinemia
An attempt was made to relate newborn anemia and hyperbilirubinemia to the SHR pattern. However, hemoglobin level, hematocrit, and bilirubin level were obtained on less than half the newborns in this series. Seven newborns had positive direct Coombs tests. Five of these were ABO incompatible, one was an Rh (Du) incompatible and one was a Lewis incompatible. Of these seven, none had a serum bilirubin greater than 16 |xmol/liter and no hemoglobin fell below 10 g. Four of the seven were in the NSHR group. DISCUSSION
The SHR pattern has the characteristics of decreased short-term variability and sine waves occurring with a frequency of 2 to 5 cycles per minute and an amplitude of 5 to 10 bpm.1-2 Although many authors4'6-8-11-14-16 have strictly adhered to this definition, others have not. Some authors 7 ' 91217 - 19 have included cases with sine waves of an amplitude up to 40 or 60 BPM. Others7-9'10'12-13'17'18 have included cases with good short-term variability. In the present study, the strict criteria denned by Rochard et al2 and Manseau et al1 are used. Finding the SHR pattern during antepartum fetal heart monitoring in Rh incompatible pregnancies is clearly ominous. Manseau et al's1 series examined eight Rh incompatible pregnancies in which the SHR pattern was found during antepartum monitor-
Table 4.
Apgar Scores
One Minute Apgar 2*7
200
42
1043 50
79 2
ing. Seven of the fetuses died in utero. Among Rochard et al's2 125 high-risk pregnancies, 20 exhibited the SHR pattern during antepartum monitoring. In all 20 cases, Rh incompatibility existed. Eight fetuses died in utero, two had neonatal deaths, and eight others required prolonged neonatal intensive care. In a similar study by Kubli et al3 9 of 12 such fetuses died in the perinatal period. Verma et al15 found that the prognosis was worse if the antepartum SHR pattern was continuous than if it were intermittent in a study of Rh incompatible pregnancies. Mueller-Heubach et al17 reported two cases in which the SHR pattern occurred only after intrauterine transfusion. Hatjis et al14 on the other hand, reported a case in which the SHR pattern disappeared after intrauterine transfusion. The meaning of the SHR pattern during antepartum monitoring in the absence of Rh incompatibility is not clear. Sachs et al4 reported anecdotally that when the SHR pattern was found during reactive nonstress tests, the outcome was uniformly good. However, Sibai et al5 reported a case in which the SHR pattern was found during antepartum monitoring. The infant was delivered the same day and died from congestive heart failure, anemia, and thrombocytopenia. Similarly, Modanlou et al6 reported on an infant delivered after an SHR pattern was found during antepartum monitoring. The infant had severe congestive heart failure and anemia, secondary to a massive fetal-maternal transfusion. Gal et al7 reported a fetal death 10 minutes after a sinusoidal pattern was found during an oxytocin challenge test. Autopsy revealed no pathologic condition except for liver necrosis. We believe that it is important to note that in two of three cases with poor outcome, anemia and congestive heart failure were present. In that respect, these cases are similar to the Rh incompatible cases. During labor there have been six fetal or neonatal deaths associated with the SHR pattern reported. All of these are isolated case reports, so the incidence of fetal death associated with SHR pattern during labor is not known. Both deaths reported by Sibai et al5 had anemia and hydrops and the amplitude of the sine waves was 40 bpw in both cases. The deaths reported by Cibils8 and Basket and Koh9 were both associated with sine waves of increased amplitude (40 to 50 bpm). The case reported by Cruikshank10 did not fit the strict definition of SHR in that variability was present. Furthermore, the pH at birth in this case was normal, so the death may be unrelated to the sinusoidal pattern. The only two deaths that have been reported with typical (strict definition)
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AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 3
FETAL HEART RATE/Egley, Bowes, Wagner
present study confirms this relationship. Other narcotics do not appear to influence the development of the SHR pattern, nor does the administration of other medications commonly used during labor influence the occurrence of the SHR pattern. It is interesting that, although oxytocin administration is not statistically associated with the development of the SHR pattern, of the seven cases in which the SHR pattern persisted for more than 90 minutes, six of these mothers had been administered oxytocin. From the present study, no conclusion can be made regarding the relationship between fetal anemia or blood group incompatibility and the development of the SHR pattern. The SHR pattern is always ominous when found during antepartum monitoring in the Rh incompatible pregnancy. When found during antepartum monitoring and the nonsensitized pregnancy, the fetus should be investigated for evidence of congestive heart failure. Sonography might reveal fetal ascites or scalp edema in these cases.22 We believe that finding a typical SHR pattern during labor is not a sign of fetal hypoxia. However, when an atypical SHR pattern is present (sine waves with an amplitude greater than 15 bpm), fetal scalp pH sampling should be performed.
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SHR are those reported by Sachs et al4 and Cetrulo and Schifrin.18 Possibly those cases with increased amplitude of the sine wave (greater than 10 bpm) have a worse prognosis. Indeed, Basket and Koh9 note that among 1000 monitored labors, the sinusoidal pattern with an amplitude of 5 to 10 bpm was not associated with fetal compromise. Young et al12 found a statistical correlation between the amplitude of the sine wave and the pH. When the amplitude was less than 15 bpm, the scalp pH tended to be normal; when the amplitude was greater than 15 bpm, the pH tended to be low. Larger series of SHR pattern during labor do not support the contention that the SHR pattern is ominous. Johnson et al11 reported on 30 SHR patterns during labor, Young et al12 on 16, and Gray et al13 on 17. The neonatal outcome was uniformly good in these cases. The present series adds 54 cases with uniformly good outcome. There was no statistically significant difference in the incidence of depressed 1-minute or 5-minute Apgar scores between the SHR group and the NSHR group in the present series. However, the Apgar score may not reflect the fetal condition during an episode of SHR pattern because only ten of the fetuses were delivered within 10 minutes of a sinusoidal pattern. In the series of 30 SHR cases reported by Johnson et al,11 no 5-minute Apgar score was depressed and in only four cases was the 1-minute Apgar score depressed (three of these had been delivered by midforceps). The presence of meconium during labor is believed to be a sign of fetal hypoxia. In the present series there is no relationship between the SHR pattern and the presence of meconium. Acceleration of the fetal heart is known to be associated with fetal well-being.21 Johnson et al11 found that when the SHR pattern was present, 93% of cases exhibited acceleration of the fetal heart. In the present series 75.9% of cases in the SHR group exhibited acceleration of the fetal heart rate compared with 80.3% in the NSHR group (not significant). Fetal scalp pH sampling was performed on only three of the SHR cases. In each case the pH was above 7.30. Young et al12 were able to perform scalp pH sampling on 11 fetuses during episodes of SHR, and four of these were acidotic. However, three of the four acidotic fetuses exhibited sine waves with an amplitude greater than 15 bpm. Johnson et al11 sampled the scalp pH on four fetuses exhibiting the SHR pattern and found no value less than 7.29. Three fetal monitoring patterns have been shown to be signs of fetal distress:21 late decelerations, severe variable decelerations, and decreased shortterm variability. The present study shows that statistically there is no significant increase in the incidence of these three patterns in the SHR group compared with the NSHR group. Gray et al13 nicely demonstrated the relationship between alphaprodine administration during labor and the development of the SHR pattern. The
REFERENCES
1. Manseau P, Vaquier J, Chavinie J, et al: Le rythme cardiaque foetal sinusoidal. Aspect evocateur de souffrance foetale au course de la grossese. J Gynecol Obstet Biol Reprod 1: 343-352, 1972 2. Rochard F, Schifrin BS, Goupil F, et al: Non-stressed fetal heart rate monitoring in the antepartum period. Am J Obstet Gynecol 126:699-705, 1976 3. Kubli F, Ruttgers H, Hallor U, et al: Die antepartale fetale herfrequenz; II. Verhalten von Grundfrequenz, fluktuation and dezerationen bei antepartalem fruchttod. Geburtshilfe Perinatol 176:309-313, 1972 4. Sachs DA, Bell KE, Schwimmer WB, et al: Sinusoidal fetal heart rate pattern with intrapartum fetal death. J Reprod Med 24:171-173, 1980 5. Sibai B, Lipshitz J, Schneider JM, et al: Sinusoidal fetal heart rate pattern. Obstet Gynecol 55:637-642, 1980 6. Modanlou HD, Freeman RK, Oritz O, et al: Sinusoidal fetal heart rate pattern and severe fetal anemia. Obstet Gynecol 49:537-541, 1977 7. Gal D, Jacobson LM, Ser H, et al: Sinusoidal pattern: An alarming sign of fetal distress. Am J Obstet Gynecol 132: 903-905, 1978 8. Cibils LA: Clinical significance of fetal heart rate patterns during labor: Agonal patterns. Am J Obstet Gynecol 129:833-841, 1977 9. Basket TF, Koh KS: Sinusoidal fetal heart pattern: A sign of fetal hypoxia. Obstet Gynecol 44:379-382, 1974 10. Cruikshank DP: An unusual fetal heart rate pattern. Am J Obstet Gynecol 132:101-102, 1978 11. Johnson TR, Compton AA, Rotmensch J, et al: Significance of the sinusoidal fetal heart rate pattern. Am J Obstet Gynecol 139:446-453, 1981 12. Young BK, Katz M, Wilson SJ: Sinusoidal fetal heart rate: Clinical significance. Am J Obstet Gynecol 136:587593, 1980 13. Gray JH, Cudmore DW, Luther EB, et al: Sinusoidal fetal heart pattern associated with alphaprodine administration. Obstet Gynecol 52:678-681, 1978
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18. Cetrulo CL, Schifrin BS: Fetal heart rate patterns preceding death in utero. Obstet Gynecol 48:521-527, 1976 19. Katz M, Wilson SJ, Young BK: Sinusoidal fetal heart rate: Continuous tissue pH studies. Am J Obstet Gynecol 136: 594-596, 1980 20. Walker J: Fetal distress. Am J Obstet Gynecol 77:94-102, 1959 21. Freeman RK, Garite TJ: Fetal Heart Rate Monitoring. Baltimore: Williams & Wilkins, 1981, pp 63-79 22. Schneider EP, Troppler PT: The variable deceleration, prolonged deceleration and sinusoidal fetal heart rate. Clin Obstet Gynecol 29:64-71, 1986
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14. Hatjis CG, Mennuti MT, Sachs LM, et al: Resolution of a sinusoidal fetal heart pattern following intrauterine transfusion. Am J Obstet Gynecol 132:109-111, 1978 15. Verma U, Tejani N, Weiss RR, et al: Sinusoidal fetal heart rate patterns in severe Rh disease. Obstet Gynecol 55: 666-669, 1980 16. Elliott JP, Modanlou HD, O'Keefe DF, et al: Significance of fetal and neonatal sinusoidal heart rate pattern: Further clinical observations in Rh incompatibility. Am J Obstet Gynecol 138:227-230, 1980 17. Mueller-Heubach E, Cartis SN, Edelston DL: Sinusoidal fetal heart rate following intrauterine transfusion. Obstet Gynecol 52.43S-46S, 1978
May 1991
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May 1991
SINUSOIDAL FETAL HEART RATE PATTERN DURING LABOR Charles C. Egley, M.D., Watson A. Bowes, Jr., M.D., and Denise Wagner, R.N.
ABSTRACT
The sinusoidal heart rate (SHR) pattern, when found during antepartum monitoring of the rhesus immunized pregnancy, is ominous.1-3 However, there is some question of the seriousness of the sinusoidal pattern when it is found during antepartum monitoring in the absence of rhesus isoimmunization.4-7 The meaning of the SHR pattern during labor is unclear. Six perinatal deaths have been reported to be associated with this pattern.4-5-8-10 However, when the SHR pattern during labor is examined in larger series,11-13 the neonatal outcome is nearly uniformly good. It is emphasized that the present report includes only cases of typical sinusoidal pattern (Fig. 1), defined as sine waves with a frequency of 2 to 5 per minute, an amplitude of 5 to 10 beats per minute (bpm), and short-term variability of less than 2 bpm. We examine the incidence of SHR pattern during labor, what drugs and maternal conditions influence the incidence of this pattern, the condition of the fetus who exhibits this pattern, and the relationship between the SHR pattern during labor and other fetal heart monitor patterns.
Downloaded by: National University of Singapore. Copyrighted material.
Of 1280 consecutive fetuses monitored internally with a scalp electrode for at least 10 minutes during labor, 54 (4.2%) demonstrated the sinusoidal heart rate (SHR) pattern. Seven of these demonstrated the SHR pattern for more than 90 minutes. In six of these seven cases, the SHR pattern occurred during oxytocin administration. The SHR group did not differ from the 1226 fetuses not demonstrating the SHR pattern (NSHR group) in Apgar scores, incidence of other fetal heart rate abnormalities, or passage of meconium. The scalp pH was obtained from three fetuses in the SHR group and was above 7.30 in each. Alphaprodine administration during labor was associated with development of the SHR pattern, whereas other narcotic administration was not. The significance of "atypical" SHR pattern with increased amplitude is discussed, along with the need to adhere to strict definition of the SHR pattern.
MATERIALS AND METHODS
All fetal heart rate (FHR) tracings obtained with scalp electrodes (Corometrics spiral FECG electrode, Corometrics, Wallingford, CT) from fetuses of mothers laboring during a 6-month period between January 1, 1977, and June 30, 1977, were reviewed. Included in this study were only those fetuses of 30 weeks or greater gestation who were monitored with scalp electrodes for at least 10 minutes. In all, 1280 cases fit these criteria. The SHR is defined as typical sine waves with (1) a frequency of 2 to 5 per minute, (2) an amplitude of 5 to 10 bpm, and (3) short-term variability of less than 2 bpm (Fig. 1). Among the 1280 cases reviewed, 54 (4.2%) demonstrated the SHR pattern. These 54 cases (SHR group) were compared with the 1226 cases not demonstrating this pattern (NSHR group). Data were obtained from review of maternal and neonatal records. Chi-square analysis was used unless fewer than five cases were present in any one cell. In the event
St. Francis Medical Center, Peoria, Illinois and The Division of Maternal and Fetal Medicine, Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, North Carolina Reprint requests: Dr. Egley, University of North Carolina, Wake AHEC, 3000 New Bern Ave., Raleigh, NC 27610 Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
197
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 3 1
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Typical sinusoidal fetal heart rate pattern.
of fewer than five cases in any one cell, exact probability was calculated. The study period (1977) was used because we believe that little was known about the SHR during labor at that time. Thus, the presence of the SHR pattern should not have influenced patient management. Careful record review reflects this, in that there was no mention of the SHR pattern among the records of the 54 cases. RESULTS
SHR pattern occurred in a labor, it persisted for a mean of 47 minutes. This figure is skewed, however, by two cases in which the pattern persisted for more than 200 minutes. The seven cases in which the SHR pattern persisted for more than 90 minutes were analyzed separately. Among these seven cases there was no evidence of ABO or Rh isoimmunization or maternal complications (except for two mothers who gained more than 40 pounds during pregnancy). All seven cases had 1- and 5-minute Apgar scores greater than seven. Only one fetus passed meconium during labor. In six of the seven cases, however, it was found that oxytocin was used to augment or induce labor.
Incidence
The sinusoidal pattern was found in 54 (4.2%) of the 1280 cases studied. It was observed, however, that the SHR group was monitored with a scalp electrode for an average of 297 minutes compared with an average of only 180 minutes for the NSHR group. Therefore finding an SHR pattern may be a function of how long the fetus is monitored with a scalp electrode. Length of Time Sinusoidal
The length of time that the sinusoidal pattern persisted in a given labor varied from less than 1 minute to more than 4 hours (Table 1). When the
Length of Time Sinusoidal to Delivery
In only four cases did the sinusoidal pattern occur with 2 minutes of delivery. All four of these cases had 1- and 5-minute Apgar scores above seven and only one of the four had meconium passage at delivery. In six other cases the sinusoidal pattern was present within 10 minutes of delivery and in one other case the sinusoidal pattern was present within 15 minutes of delivery. In the other 43 cases the sinusoidal pattern had ended more than 15 minutes before delivery. Thus, Apgar scores may not reflect what the fetal condition had been during the time period the SHR pattern existed.
Fetal Scalp pH Table 1.
Length of Time the SHR Pattern Exists
Length of Time Sinusoidal (minutes)
198
Less than 10 10-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90 91-100 101-200 More than 200
No. Cases
12 9 5 4 6 3 1 6 1 2 3 2
Fetal scalp pH sampling was performed on three of the 54 cases during or within 5 minutes after an episode of SHR. The indication for the pH sampling was decreased short-term variability in all three cases and each time the pH was above 7.30.
Influence of Medications
The influence of medications commonly administered during labor was examined (Table 2). Although other medications (such as antibiotics, tranquilizers, prochlorperazine, magnesium sulfate, phenytoin) were administered during labor, the fre-
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May 1991
FETAL HEART RATE/Egley, Bowes, Wagner Table 2.
Influence of Drugs on the SHR Pattern SHR Group (n = 54)
NSHR Group (n = 7226)
Drug*
No.
%
No.
%
Significance
Alphaprodine Morphine sulphate Meperidine Methotrimeprazine/propiomazine All narcotics Meperidine/hydroxyzine Hydroxyzine Oxytocin
9 3 16 3 29 6 23 17
16.7 5.6 29.6 5.6 53.7 11.1 42.6 31.1
86 25 257 48 418 174 478 331
7.0 2.0 21.0 3.9 34.1 14.2 40.0 27.0
p =s0.01 p =0.09 NS NS p *SO.O1 NS NS NS
*Alone or in combination.
Meconium
Meconium was present either during labor or at delivery in 13 of 54 (24%) SHR cases and present in 257 of 1226 (21%) nonsinusoidal cases. There is not a statistically significant association. Other FHR Patterns
The SHR group did not differ statistically from the NSHR group in the incidence of variable decelerations, severe variable decelerations, accelerations, tachycardia, bradycardia, head compression patterns, or late decelerations (Table 3). Arrhythmias were suspected from the FHR tracing in 4% of the sinusoidal group and 3.9% of the NSHR group. Short-term variability was decreased or absent in all SHR cases during an episode of the SHR pattern. When decreased short-term variability was examined outside periods of sinusoidal pattern, it was found in 13% of SHR cases and in 14.7% of NSHR cases.
Table 3.
Other FHR Patterns
Maternal Condition Pattern
In none of the 54 cases with the SHR pattern did the mother exhibit hypertension, third trimester bleeding, significant proteinuria, diabetes, or less than 15 pound weight gain during pregnancy. Two of the 54 (3.7%) SHR mothers had heart disease, whereas 20 of the 1226 (1.6%) NSHR mothers had heart disease during pregnancy. Two of the 54 (3.7%) SHR mothers had anemia on admission, whereas 42 of the 1226 (3.4%) NSHR mothers were anemic.
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quency of administration was too low to generate meaningful statistics. Methotrimeprazine (Levoprome) and propiomazine (Largon) were always used as a combination in this study. In no instance was either drug administered alone. Meperidine (Demerol) and hydroxyzine (Vistaril) are examined as a combination because of the high frequency of administration of this combination in this series. The relationship between alphaprodine administration during labor and development of the SHR pattern is significant. Other narcotics did not significantly increase the occurrence of the SHR pattern. Furthermore, when the cases of SHR associated with morphine sulfate were analyzed, it was found that the morphine sulfate was administered after the SHR pattern had emerged in two. Thus, although there was an association between alphaprodine use and development of the SHR pattern, no such association was found with morphine sulfate, meperidine, or propiomazine. Hydroxyzine, either alone or in combination with other drugs, appears to have no influence on development of the SHR pattern. There appears to be no statistical association between oxytocin use and the SHR pattern, although six of the seven cases in which the SHR pattern persisted for more than 90 minutes were on oxytocin at the time the SHR pattern appeared.
Variable decelerations Accelerations Decreased short-term variability* Tachycardia 2=160 bpm Head compression Bradycardia ^ 1 2 0 bpm Late decelerations Severe variable decelerations Suspect arrhythmia =5 bpm lasting 5=10 minutes.
SHR Group (n = 54) (%)
NSHR Group (n = 1226) (%)
72.2 75.9 13.0 5.5 5.6 9.2 1.8 5.5 4.0
77.0 80.3 14.2 5.4 5.7 10.2 2.0 4.2 3.9
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Apgar Scores
Table 5.
Depressed 1-minute Apgar scores (less than 7) were found in 3 of 54 (5.5%) sinusoidal cases and 64 of 1226 (5.2%) NSHR cases (Table 4). Depressed 5-minute Apgar scores were found in 1 of 54 (1.9%) SHR cases and 14 of 1,226 (1.1%) NSHR cases. Statistically, the difference is not significant at either 1 or 5 minutes. Gestation
Gestational assessment was made on each newborn. The SHR group did not differ significantly from the NSHR group in gestational distribution (Table 5). Anemia and Hyperbilirubinemia
An attempt was made to relate newborn anemia and hyperbilirubinemia to the SHR pattern. However, hemoglobin level, hematocrit, and bilirubin level were obtained on less than half the newborns in this series. Seven newborns had positive direct Coombs tests. Five of these were ABO incompatible, one was an Rh (Du) incompatible and one was a Lewis incompatible. Of these seven, none had a serum bilirubin greater than 16 |xmol/liter and no hemoglobin fell below 10 g. Four of the seven were in the NSHR group. DISCUSSION
The SHR pattern has the characteristics of decreased short-term variability and sine waves occurring with a frequency of 2 to 5 cycles per minute and an amplitude of 5 to 10 bpm.1-2 Although many authors4'6-8-11-14-16 have strictly adhered to this definition, others have not. Some authors 7 ' 91217 - 19 have included cases with sine waves of an amplitude up to 40 or 60 BPM. Others7-9'10'12-13'17'18 have included cases with good short-term variability. In the present study, the strict criteria denned by Rochard et al2 and Manseau et al1 are used. Finding the SHR pattern during antepartum fetal heart monitoring in Rh incompatible pregnancies is clearly ominous. Manseau et al's1 series examined eight Rh incompatible pregnancies in which the SHR pattern was found during antepartum monitor-
Table 4.
Apgar Scores
One Minute Apgar 2*7
200
42
1043 50
79 2
ing. Seven of the fetuses died in utero. Among Rochard et al's2 125 high-risk pregnancies, 20 exhibited the SHR pattern during antepartum monitoring. In all 20 cases, Rh incompatibility existed. Eight fetuses died in utero, two had neonatal deaths, and eight others required prolonged neonatal intensive care. In a similar study by Kubli et al3 9 of 12 such fetuses died in the perinatal period. Verma et al15 found that the prognosis was worse if the antepartum SHR pattern was continuous than if it were intermittent in a study of Rh incompatible pregnancies. Mueller-Heubach et al17 reported two cases in which the SHR pattern occurred only after intrauterine transfusion. Hatjis et al14 on the other hand, reported a case in which the SHR pattern disappeared after intrauterine transfusion. The meaning of the SHR pattern during antepartum monitoring in the absence of Rh incompatibility is not clear. Sachs et al4 reported anecdotally that when the SHR pattern was found during reactive nonstress tests, the outcome was uniformly good. However, Sibai et al5 reported a case in which the SHR pattern was found during antepartum monitoring. The infant was delivered the same day and died from congestive heart failure, anemia, and thrombocytopenia. Similarly, Modanlou et al6 reported on an infant delivered after an SHR pattern was found during antepartum monitoring. The infant had severe congestive heart failure and anemia, secondary to a massive fetal-maternal transfusion. Gal et al7 reported a fetal death 10 minutes after a sinusoidal pattern was found during an oxytocin challenge test. Autopsy revealed no pathologic condition except for liver necrosis. We believe that it is important to note that in two of three cases with poor outcome, anemia and congestive heart failure were present. In that respect, these cases are similar to the Rh incompatible cases. During labor there have been six fetal or neonatal deaths associated with the SHR pattern reported. All of these are isolated case reports, so the incidence of fetal death associated with SHR pattern during labor is not known. Both deaths reported by Sibai et al5 had anemia and hydrops and the amplitude of the sine waves was 40 bpw in both cases. The deaths reported by Cibils8 and Basket and Koh9 were both associated with sine waves of increased amplitude (40 to 50 bpm). The case reported by Cruikshank10 did not fit the strict definition of SHR in that variability was present. Furthermore, the pH at birth in this case was normal, so the death may be unrelated to the sinusoidal pattern. The only two deaths that have been reported with typical (strict definition)
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AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 3
FETAL HEART RATE/Egley, Bowes, Wagner
present study confirms this relationship. Other narcotics do not appear to influence the development of the SHR pattern, nor does the administration of other medications commonly used during labor influence the occurrence of the SHR pattern. It is interesting that, although oxytocin administration is not statistically associated with the development of the SHR pattern, of the seven cases in which the SHR pattern persisted for more than 90 minutes, six of these mothers had been administered oxytocin. From the present study, no conclusion can be made regarding the relationship between fetal anemia or blood group incompatibility and the development of the SHR pattern. The SHR pattern is always ominous when found during antepartum monitoring in the Rh incompatible pregnancy. When found during antepartum monitoring and the nonsensitized pregnancy, the fetus should be investigated for evidence of congestive heart failure. Sonography might reveal fetal ascites or scalp edema in these cases.22 We believe that finding a typical SHR pattern during labor is not a sign of fetal hypoxia. However, when an atypical SHR pattern is present (sine waves with an amplitude greater than 15 bpm), fetal scalp pH sampling should be performed.
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SHR are those reported by Sachs et al4 and Cetrulo and Schifrin.18 Possibly those cases with increased amplitude of the sine wave (greater than 10 bpm) have a worse prognosis. Indeed, Basket and Koh9 note that among 1000 monitored labors, the sinusoidal pattern with an amplitude of 5 to 10 bpm was not associated with fetal compromise. Young et al12 found a statistical correlation between the amplitude of the sine wave and the pH. When the amplitude was less than 15 bpm, the scalp pH tended to be normal; when the amplitude was greater than 15 bpm, the pH tended to be low. Larger series of SHR pattern during labor do not support the contention that the SHR pattern is ominous. Johnson et al11 reported on 30 SHR patterns during labor, Young et al12 on 16, and Gray et al13 on 17. The neonatal outcome was uniformly good in these cases. The present series adds 54 cases with uniformly good outcome. There was no statistically significant difference in the incidence of depressed 1-minute or 5-minute Apgar scores between the SHR group and the NSHR group in the present series. However, the Apgar score may not reflect the fetal condition during an episode of SHR pattern because only ten of the fetuses were delivered within 10 minutes of a sinusoidal pattern. In the series of 30 SHR cases reported by Johnson et al,11 no 5-minute Apgar score was depressed and in only four cases was the 1-minute Apgar score depressed (three of these had been delivered by midforceps). The presence of meconium during labor is believed to be a sign of fetal hypoxia. In the present series there is no relationship between the SHR pattern and the presence of meconium. Acceleration of the fetal heart is known to be associated with fetal well-being.21 Johnson et al11 found that when the SHR pattern was present, 93% of cases exhibited acceleration of the fetal heart. In the present series 75.9% of cases in the SHR group exhibited acceleration of the fetal heart rate compared with 80.3% in the NSHR group (not significant). Fetal scalp pH sampling was performed on only three of the SHR cases. In each case the pH was above 7.30. Young et al12 were able to perform scalp pH sampling on 11 fetuses during episodes of SHR, and four of these were acidotic. However, three of the four acidotic fetuses exhibited sine waves with an amplitude greater than 15 bpm. Johnson et al11 sampled the scalp pH on four fetuses exhibiting the SHR pattern and found no value less than 7.29. Three fetal monitoring patterns have been shown to be signs of fetal distress:21 late decelerations, severe variable decelerations, and decreased shortterm variability. The present study shows that statistically there is no significant increase in the incidence of these three patterns in the SHR group compared with the NSHR group. Gray et al13 nicely demonstrated the relationship between alphaprodine administration during labor and the development of the SHR pattern. The
REFERENCES
1. Manseau P, Vaquier J, Chavinie J, et al: Le rythme cardiaque foetal sinusoidal. Aspect evocateur de souffrance foetale au course de la grossese. J Gynecol Obstet Biol Reprod 1: 343-352, 1972 2. Rochard F, Schifrin BS, Goupil F, et al: Non-stressed fetal heart rate monitoring in the antepartum period. Am J Obstet Gynecol 126:699-705, 1976 3. Kubli F, Ruttgers H, Hallor U, et al: Die antepartale fetale herfrequenz; II. Verhalten von Grundfrequenz, fluktuation and dezerationen bei antepartalem fruchttod. Geburtshilfe Perinatol 176:309-313, 1972 4. Sachs DA, Bell KE, Schwimmer WB, et al: Sinusoidal fetal heart rate pattern with intrapartum fetal death. J Reprod Med 24:171-173, 1980 5. Sibai B, Lipshitz J, Schneider JM, et al: Sinusoidal fetal heart rate pattern. Obstet Gynecol 55:637-642, 1980 6. Modanlou HD, Freeman RK, Oritz O, et al: Sinusoidal fetal heart rate pattern and severe fetal anemia. Obstet Gynecol 49:537-541, 1977 7. Gal D, Jacobson LM, Ser H, et al: Sinusoidal pattern: An alarming sign of fetal distress. Am J Obstet Gynecol 132: 903-905, 1978 8. Cibils LA: Clinical significance of fetal heart rate patterns during labor: Agonal patterns. Am J Obstet Gynecol 129:833-841, 1977 9. Basket TF, Koh KS: Sinusoidal fetal heart pattern: A sign of fetal hypoxia. Obstet Gynecol 44:379-382, 1974 10. Cruikshank DP: An unusual fetal heart rate pattern. Am J Obstet Gynecol 132:101-102, 1978 11. Johnson TR, Compton AA, Rotmensch J, et al: Significance of the sinusoidal fetal heart rate pattern. Am J Obstet Gynecol 139:446-453, 1981 12. Young BK, Katz M, Wilson SJ: Sinusoidal fetal heart rate: Clinical significance. Am J Obstet Gynecol 136:587593, 1980 13. Gray JH, Cudmore DW, Luther EB, et al: Sinusoidal fetal heart pattern associated with alphaprodine administration. Obstet Gynecol 52:678-681, 1978
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18. Cetrulo CL, Schifrin BS: Fetal heart rate patterns preceding death in utero. Obstet Gynecol 48:521-527, 1976 19. Katz M, Wilson SJ, Young BK: Sinusoidal fetal heart rate: Continuous tissue pH studies. Am J Obstet Gynecol 136: 594-596, 1980 20. Walker J: Fetal distress. Am J Obstet Gynecol 77:94-102, 1959 21. Freeman RK, Garite TJ: Fetal Heart Rate Monitoring. Baltimore: Williams & Wilkins, 1981, pp 63-79 22. Schneider EP, Troppler PT: The variable deceleration, prolonged deceleration and sinusoidal fetal heart rate. Clin Obstet Gynecol 29:64-71, 1986
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14. Hatjis CG, Mennuti MT, Sachs LM, et al: Resolution of a sinusoidal fetal heart pattern following intrauterine transfusion. Am J Obstet Gynecol 132:109-111, 1978 15. Verma U, Tejani N, Weiss RR, et al: Sinusoidal fetal heart rate patterns in severe Rh disease. Obstet Gynecol 55: 666-669, 1980 16. Elliott JP, Modanlou HD, O'Keefe DF, et al: Significance of fetal and neonatal sinusoidal heart rate pattern: Further clinical observations in Rh incompatibility. Am J Obstet Gynecol 138:227-230, 1980 17. Mueller-Heubach E, Cartis SN, Edelston DL: Sinusoidal fetal heart rate following intrauterine transfusion. Obstet Gynecol 52.43S-46S, 1978
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