British Journal of Obstetrics and Gynaecology
November 1991, Vol. 98, pp. 1093-1101
The prevalence, aetiology and clinical significance of pseudo-sinusoidal fetal heart rate patterns in labour KARL W. MURPHY, VIRGINIA RUSSELL, AMANDA COLLINS, PAUL JOHNSON Abstract
Objective--To investigate the prevalence of sinusoidal and pseudo-sinusoidal fetal heart rate (FHR) patterns in labour and the relation between the characteristics of the FHR pattern and fetal outcome. Design-A prospective observational study over a &month period in which all women who had continuous FHR monitoring in labour had their intrapartum cardiotocographs (CTGs)scrutinized for the presence of sinusoidal or pseudosinusoidal FHR patterns. Setting-John Radcliffe Hospital, Oxford. Subjects-1520 women who had fetal monitoring during labour for various reasons, Main outcome measures-Both internal (electrocardiographic) and external (ultrasound) recordings of the FHR were analysed. Abnormal FHR patterns were related to obstetric characteristics and fetal outcome in terms of Apgar scores, umbilical artery pH and admission to the special care unit. Results-No true sinusoidal FHR patterns were observed, but pseudosinusoidal FHR patterns were found in 230 of the 1520 CTGs examined (15%). Of these, 219 were classified as minor (amplitude 5-15 beatdmin) and 11 as intermediate (amplitude 16-24 beatdmin). Major pseudo-sinusoidal FHR patterns (amplitude >24 beatdmin) were not observed. Minor pseudo-sinusoidal FHR patterns had a mean duration of 21 (SD 13) min and typically occurred once or twice early in labour. Using logistic regression analysis a significant, independent relation was demonstrated between the presence of minor pseudosinusoidal FHR patterns and the use of pethidine (RR 1-84,95% CI 1.3 to 2.59, P S beatshin) more frequently than this. These episodcs mimicked sinusoidal FHK pattcrns and were sometimes difficult to classify. Thc aims of this study wcre to report the prevalencc of sinusoidal and pseudo-sinusoidal F H R pattcrns in labour in our monitored population. to catcgorizc the different patterns observed and to explore the relation between the pattern charactcristics and fctal outcome. It was hopcd that a multivariate analysis of the factors associated with these pattcrns might shed some light on their actiology.
trocardiographic) and extcrnal (ultrasonic) rccordings of the F H R wcre analysed. Thc intrapartum CTGs were reviewcd immediatcly after thc recordings were made and the relcvant clinical data were recorded at the timc. A pseudo-sinusoidal F H R pattern has been defincd above. Only episodes which persistcd for 310 min were included. Pseudo-sinusoidal patterns wcrc classified as minor whcn the amplitudc of the oscillations was 5-15 b e a t s h i n , intcrmediate at l C ~ 2 4bcatslmin and major whcn the amplitude was 3 2 5 . Cyclc frequency was 2-5 cyclcslmin Cor minor and intermcdiate patterns and 1-2 cycleshin for major patterns. Intrapartum ultrasonography to look for fctal sucking or mouthing movements was undertaken (subjcct to availability) in a small numbcr of wonicn during the pscudo-sinusoidal cpisodcs. Neonatal hcart rate recordings. obtained from skin electrodcs placcd over the infant's chest, wcrc also performed in a fcw of the subjects in whom pscudo-sinusoidal F H R episodes had bccn observed in labour. Every tcnth woman who was monitored in labour during the &month study period and who did not have a sinusoidal o r pseudo-sinusoidal FHR pattcrn was choscn as a control. A total of 100 controls were obtained in this way. Obstctric characteristics and indices o f fctal outcomc in thc study and control groups wcrc recorded. Umbilical artery blood gas and pH mcasurements wcrc made whenevcr there was cvidence of fctal distress or when an operative o r instrumental dclivcry had been pcrformed. Thc CTGs were classified as normal o r abnormal by the rcvicwcrs according to the criteria suggcsted by Steer et 01. (1989). In addition, uterine hyperstimulation was diagnosed when morc than 15 contractions wcrc present during a 30-min period.
Subjects and methods
This prospectivc study was carried out at thc John Radcliffc Hospital during a &month period (11 September 1987 to 29 February 1988). Thc study group comprised all women who had fctal monitoring in labour during this time ( n = 1520). During thc study period 49% o f all labours were monitored and the indications for monitoring werc as follows: oxytocin (31%). hypertcnsive disorders and intrauterine growth retardation (22%), epidural analgcsia (IS%), breech (4'%), irrcgular F H R on auscultation (3%) and others (16%). Both intcrnal (elec-
Stritisticul attalysis
Univariatc analyses to comparc results bctwccn the study and thc control groups used the x'. Fishcr's cxact and the Mann-Whitney U tcsts. Multivariate analysis (logistic regression analysis) was then pcrformcd to examine the association between thc prcscncc o f pseudo-sinusoidal F H R patterns in lahour and thc following variables: the presence o f fetal slccp cycles, induction of labour, mcconium staincd amniotic fluid, prostaglandin (to inducc labour), pethidine o r epidural analgesia. oxytocin to induce or to aug-
Pseudo-sinusoidal FHR patterns Normal baseline Minor pseudo-sinusoidal variability FHA pattern 1
. . . .
...
....*
... . -10
.
.,, .
.i.ll,
, 1.
.
. .
mins
Fig. 1. Minor pscudo-sinusoidalfetal heart ratc (FHR) pattcrn. The first half of this recording shows normal baseline variability. The second half shows regular oscillations in thc baseline FHR. The oscillations have an mplitude of 5-10 bcats/min and a frcqucncy of approximately 5 cycleshin. Fctal outcomc was normal. FHR: internal ECG recording. Tocograph: cxtcrnal recording. Paper spccd: I cmlmin.
ment labour, uterine hyperstimulation, the duration of labour, cord encirclement at delivery, abnormal CTG. Apgar scores and umbilical artery pH. The number of women who received pethidinc during the 3O-min period immediately preceding the pseudo-sinusoidal cpisode was also recorded, other than this pethidine was recorded only as a yes or no variable.
Results During the &month study period a total of 1520
CTGs wcre reviewed. There were no intrapartum sinusoidal FHR patterns but 230 pseudo-
1095
(Fig. 2). No intrapartum major pseudosinusoidal F H R patterns were found, but an example of an antepartum one, observed in a fetus who bled following cordocentesis, is shown in Fig. 3. Most of the minor (94%) and intermediate (91%) pseudo-sinusoidal FHR patterns were observed during the first stage of labour. The mean interval from the last pattern to delivery was 230 (SD 176) min in the minor pseudosinusoidal group and 295 (SD 149) min in the intermediate pseudo-sinusoidal group. The median number of minor pseudo-sinusoidal episodes per subject in the study was 2. The mean duration of the minor pseudo-sinusoidal episodes was 21 (SD 13 range lU--lOO min). Table 1 shows the frequency distribution of minor pseudo-sinusoidal episodes per subject: the largest group of 42% had only a single episode during labour. Although the duration of labour monitored varied, data were available for the greater part of labour for most women. Minor pseudo-sinusoidal F H R patterns frequently coincided with quiet fetal sleep cycles: the episodes occurred during a quiet sleep cycle in 105 (48%), during an active sleep cycle in 11 ( 5 % ) and during non-determinate sleep patterns in the remainder (47%). The obstetric characteristics of the minor pseudo-sinusoidal group ( n = 219) and the control group ( n = 100) were comparcd (Table 2). Factors which were statistically significantly different between the pseudo-sinusoidal and the control groups included the following: (i) the
sinusoidal FHR pattcrns were identified during this time (incidence 15%). Of these, 219 were minor (Fig. 1 ) and 11 were intermediate patterns i
. II
. ..
.
w
'
_-
' 2 1
-10
Fig. 2. Intcrmcdiate pseudo-sinusoidal FHR pattern bhowing oscillations with an amplitudc of 15-20 heats/ min and a frcqucncy of 2-3 cyclcs/min. The baseline FHR increased during thc oscillatory period. This pattcrn was caused by non-nutritive, fetal sucking. Fctal outcome was normal. FHR: internal ECG recording. Tocograph: cxternal rccording. Paper speed: I cm/min.
mins-
Fig. 3. Major pseudo-sinusoidal FHK pattern showing oscillations with an amplitude of 10-60 bcatdmin and a frequency of 1-2 cycles/min. This pattern followed an antcpartum cordocentcsis to nieasurc fctal platclcts. Acute cord haemorrhagc occurrcd and a hypovolacmic infant was born by emergency caesarean section. FHR: intcrnal ECG recording. Tocograph: external recording. Paper specd: 1 cm/ min.
1096
K. W.Murphy et al.
Table 1. Frequency distribution of minor pscudosinusoidal FHR patterns in the study group (n = 219) No. of minor pseudo-sinusoidal episodes per subject
No. of subjects
1 2 3 4+
Total
92 (42%) 71 (32%) 38 (17%) 18 (8%) 219 (100%)
percentage of womcn who received 100 mg of intramuscular pethidine: 60% vs 36% (x' with Yates' correction = 15.3, P
November 1991, Vol. 98, pp. 1093-1101
The prevalence, aetiology and clinical significance of pseudo-sinusoidal fetal heart rate patterns in labour KARL W. MURPHY, VIRGINIA RUSSELL, AMANDA COLLINS, PAUL JOHNSON Abstract
Objective--To investigate the prevalence of sinusoidal and pseudo-sinusoidal fetal heart rate (FHR) patterns in labour and the relation between the characteristics of the FHR pattern and fetal outcome. Design-A prospective observational study over a &month period in which all women who had continuous FHR monitoring in labour had their intrapartum cardiotocographs (CTGs)scrutinized for the presence of sinusoidal or pseudosinusoidal FHR patterns. Setting-John Radcliffe Hospital, Oxford. Subjects-1520 women who had fetal monitoring during labour for various reasons, Main outcome measures-Both internal (electrocardiographic) and external (ultrasound) recordings of the FHR were analysed. Abnormal FHR patterns were related to obstetric characteristics and fetal outcome in terms of Apgar scores, umbilical artery pH and admission to the special care unit. Results-No true sinusoidal FHR patterns were observed, but pseudosinusoidal FHR patterns were found in 230 of the 1520 CTGs examined (15%). Of these, 219 were classified as minor (amplitude 5-15 beatdmin) and 11 as intermediate (amplitude 16-24 beatdmin). Major pseudo-sinusoidal FHR patterns (amplitude >24 beatdmin) were not observed. Minor pseudo-sinusoidal FHR patterns had a mean duration of 21 (SD 13) min and typically occurred once or twice early in labour. Using logistic regression analysis a significant, independent relation was demonstrated between the presence of minor pseudosinusoidal FHR patterns and the use of pethidine (RR 1-84,95% CI 1.3 to 2.59, P S beatshin) more frequently than this. These episodcs mimicked sinusoidal FHK pattcrns and were sometimes difficult to classify. Thc aims of this study wcre to report the prevalencc of sinusoidal and pseudo-sinusoidal F H R pattcrns in labour in our monitored population. to catcgorizc the different patterns observed and to explore the relation between the pattern charactcristics and fctal outcome. It was hopcd that a multivariate analysis of the factors associated with these pattcrns might shed some light on their actiology.
trocardiographic) and extcrnal (ultrasonic) rccordings of the F H R wcre analysed. Thc intrapartum CTGs were reviewcd immediatcly after thc recordings were made and the relcvant clinical data were recorded at the timc. A pseudo-sinusoidal F H R pattern has been defincd above. Only episodes which persistcd for 310 min were included. Pseudo-sinusoidal patterns wcrc classified as minor whcn the amplitudc of the oscillations was 5-15 b e a t s h i n , intcrmediate at l C ~ 2 4bcatslmin and major whcn the amplitude was 3 2 5 . Cyclc frequency was 2-5 cyclcslmin Cor minor and intermcdiate patterns and 1-2 cycleshin for major patterns. Intrapartum ultrasonography to look for fctal sucking or mouthing movements was undertaken (subjcct to availability) in a small numbcr of wonicn during the pscudo-sinusoidal cpisodcs. Neonatal hcart rate recordings. obtained from skin electrodcs placcd over the infant's chest, wcrc also performed in a fcw of the subjects in whom pscudo-sinusoidal F H R episodes had bccn observed in labour. Every tcnth woman who was monitored in labour during the &month study period and who did not have a sinusoidal o r pseudo-sinusoidal FHR pattcrn was choscn as a control. A total of 100 controls were obtained in this way. Obstctric characteristics and indices o f fctal outcomc in thc study and control groups wcrc recorded. Umbilical artery blood gas and pH mcasurements wcrc made whenevcr there was cvidence of fctal distress or when an operative o r instrumental dclivcry had been pcrformed. Thc CTGs were classified as normal o r abnormal by the rcvicwcrs according to the criteria suggcsted by Steer et 01. (1989). In addition, uterine hyperstimulation was diagnosed when morc than 15 contractions wcrc present during a 30-min period.
Subjects and methods
This prospectivc study was carried out at thc John Radcliffc Hospital during a &month period (11 September 1987 to 29 February 1988). Thc study group comprised all women who had fctal monitoring in labour during this time ( n = 1520). During thc study period 49% o f all labours were monitored and the indications for monitoring werc as follows: oxytocin (31%). hypertcnsive disorders and intrauterine growth retardation (22%), epidural analgcsia (IS%), breech (4'%), irrcgular F H R on auscultation (3%) and others (16%). Both intcrnal (elec-
Stritisticul attalysis
Univariatc analyses to comparc results bctwccn the study and thc control groups used the x'. Fishcr's cxact and the Mann-Whitney U tcsts. Multivariate analysis (logistic regression analysis) was then pcrformcd to examine the association between thc prcscncc o f pseudo-sinusoidal F H R patterns in lahour and thc following variables: the presence o f fetal slccp cycles, induction of labour, mcconium staincd amniotic fluid, prostaglandin (to inducc labour), pethidine o r epidural analgesia. oxytocin to induce or to aug-
Pseudo-sinusoidal FHR patterns Normal baseline Minor pseudo-sinusoidal variability FHA pattern 1
. . . .
...
....*
... . -10
.
.,, .
.i.ll,
, 1.
.
. .
mins
Fig. 1. Minor pscudo-sinusoidalfetal heart ratc (FHR) pattcrn. The first half of this recording shows normal baseline variability. The second half shows regular oscillations in thc baseline FHR. The oscillations have an mplitude of 5-10 bcats/min and a frcqucncy of approximately 5 cycleshin. Fctal outcomc was normal. FHR: internal ECG recording. Tocograph: cxtcrnal recording. Paper spccd: I cmlmin.
ment labour, uterine hyperstimulation, the duration of labour, cord encirclement at delivery, abnormal CTG. Apgar scores and umbilical artery pH. The number of women who received pethidinc during the 3O-min period immediately preceding the pseudo-sinusoidal cpisode was also recorded, other than this pethidine was recorded only as a yes or no variable.
Results During the &month study period a total of 1520
CTGs wcre reviewed. There were no intrapartum sinusoidal FHR patterns but 230 pseudo-
1095
(Fig. 2). No intrapartum major pseudosinusoidal F H R patterns were found, but an example of an antepartum one, observed in a fetus who bled following cordocentesis, is shown in Fig. 3. Most of the minor (94%) and intermediate (91%) pseudo-sinusoidal FHR patterns were observed during the first stage of labour. The mean interval from the last pattern to delivery was 230 (SD 176) min in the minor pseudosinusoidal group and 295 (SD 149) min in the intermediate pseudo-sinusoidal group. The median number of minor pseudo-sinusoidal episodes per subject in the study was 2. The mean duration of the minor pseudo-sinusoidal episodes was 21 (SD 13 range lU--lOO min). Table 1 shows the frequency distribution of minor pseudo-sinusoidal episodes per subject: the largest group of 42% had only a single episode during labour. Although the duration of labour monitored varied, data were available for the greater part of labour for most women. Minor pseudo-sinusoidal F H R patterns frequently coincided with quiet fetal sleep cycles: the episodes occurred during a quiet sleep cycle in 105 (48%), during an active sleep cycle in 11 ( 5 % ) and during non-determinate sleep patterns in the remainder (47%). The obstetric characteristics of the minor pseudo-sinusoidal group ( n = 219) and the control group ( n = 100) were comparcd (Table 2). Factors which were statistically significantly different between the pseudo-sinusoidal and the control groups included the following: (i) the
sinusoidal FHR pattcrns were identified during this time (incidence 15%). Of these, 219 were minor (Fig. 1 ) and 11 were intermediate patterns i
. II
. ..
.
w
'
_-
' 2 1
-10
Fig. 2. Intcrmcdiate pseudo-sinusoidal FHR pattern bhowing oscillations with an amplitudc of 15-20 heats/ min and a frcqucncy of 2-3 cyclcs/min. The baseline FHR increased during thc oscillatory period. This pattcrn was caused by non-nutritive, fetal sucking. Fctal outcome was normal. FHR: internal ECG recording. Tocograph: cxternal rccording. Paper speed: I cm/min.
mins-
Fig. 3. Major pseudo-sinusoidal FHK pattern showing oscillations with an amplitude of 10-60 bcatdmin and a frequency of 1-2 cycles/min. This pattern followed an antcpartum cordocentcsis to nieasurc fctal platclcts. Acute cord haemorrhagc occurrcd and a hypovolacmic infant was born by emergency caesarean section. FHR: intcrnal ECG recording. Tocograph: external recording. Paper specd: 1 cm/ min.
1096
K. W.Murphy et al.
Table 1. Frequency distribution of minor pscudosinusoidal FHR patterns in the study group (n = 219) No. of minor pseudo-sinusoidal episodes per subject
No. of subjects
1 2 3 4+
Total
92 (42%) 71 (32%) 38 (17%) 18 (8%) 219 (100%)
percentage of womcn who received 100 mg of intramuscular pethidine: 60% vs 36% (x' with Yates' correction = 15.3, P
