A randomized control study of oxytocin augmentation of labour. 2. Uterine activity

Intrauterine versus external tocodynamometry in monitoring labour: a randomised controlled clinical trial

OBJECTIVE

To investigate whether the use of intrauterine tocodynamometry versus external tocodynamometry (IT versus ET) during labour reduces operative deliveries and improves newborn outcome. As IT provides more accurate information on labour contractions, the hypothesis was that it may more appropriately guide oxytocin use than ET.

DESIGN

Randomised controlled trial.

SETTING

Two labour wards, in a university tertiary hospital and a central hospital.

POPULATION

A total of 1504 parturients with singleton pregnancies, gestational age ≥37 weeks and fetus in cephalic position: 269 women with uterine scars, 889 nulliparas and 346 parous women with oxytocin augmentation.

METHODS

Participants underwent IT (n = 736) or ET (n = 768) during the active first stage of labour.

MAIN OUTCOME MEASURES

Primary outcome: rate of operative deliveries.

SECONDARY OUTCOMES

duration of labour, amount of oxytocin given, adverse neonatal outcomes.

RESULTS

Operative delivery rates were 26.9% (IT) and 25.9% (ET) (odds ratio 1.05, 95% CI 0.84-1.32, P = 0.663). The ET to IT conversion rate was 31%. We found no differences in secondary outcomes (IT versus ET). IT reduced oxytocin use during labours with signs of fetal distress, and trial of labour after caesarean section.

CONCLUSIONS

IT did not reduce the rate of operative deliveries, use of oxytocin, or adverse neonatal outcomes, and it did not shorten labour duration.

TWEETABLE ABSTRACT

IT (versus ET) reduced oxytocin use in high-risk labours but did not influence operative delivery rate or adverse neonatal outcomes.

Factors associated with higher oxytocin requirements in labor

OBJECTIVE

To identify clinical characteristics associated with high maximum oxytocin doses in women who achieve complete cervical dilation.

METHODS

A retrospective nested case-control study was performed within a cohort of all term women at a single center between 2004 and 2008 who reached the second stage of labor. Cases were defined as women who had a maximum oxytocin dose during labor >20 mu/min, while women in the control group had a maximum oxytocin dose during labor of ≤20 mu/min. Exclusion criteria included no oxytocin administration during labor, multiple gestations, major fetal anomalies, nonvertex presentation, and prior cesarean delivery. Multiple maternal, fetal, and labor factors were evaluated with univariable analysis and multivariable logistic regression.

RESULTS

Maximum oxytocin doses >20 mu/min were administered to 108 women (3.6%), while 2864 women received doses ≤20 mu/min. Factors associated with higher maximum oxytocin dose after adjusting for relevant confounders included maternal diabetes, birthweight >4000 g, intrapartum fever, administration of magnesium, and induction of labor.

CONCLUSIONS

Few women who achieve complete cervical dilation require high doses of oxytocin. We identified maternal, fetal and labor factors that characterize this group of parturients.

High-dose versus low-dose oxytocin for augmentation of delayed labour

BACKGROUND

A major cause of failure to achieve spontaneous vaginal birth is delay in labour due to presumed inefficient uterine action. Oxytocin is given to increase contractions and high-dose regimens may potentially increase the number of spontaneous vaginal births, but as oxytocin can cause hyperstimulation of the uterus, there is a possibility of increased adverse events.

OBJECTIVES

To compare starting dose and increment dose of oxytocin for augmentation for women delayed in labour to determine whether augmentation by high-dose regimens of oxytocin improves labour outcomes and to examine the effect on both maternal/neonatal outcomes and women's birth experiences.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2013) and reference lists of retrieved studies.

SELECTION CRITERIA

We included all randomised and quasi-randomised controlled trials for women in delayed labour requiring augmentation by oxytocin comparing high-dose regimens (defined as starting dose and increment of equal to or more than 4 mU per minute) with low-dose regimens (defined as starting dose and an increment of less than 4 mU per minute). Increase interval: between 15 and 40 minutes. The separation of low- and high-dose regimens is based on an arbitrary decision.

DATA COLLECTION AND ANALYSIS

Four review authors undertook assessment of trial eligibility, risk of bias, and data extraction independently.

MAIN RESULTS

We included four studies involving 644 pregnant women. Three studies were randomised controlled trials and one trial was a quasi-randomised study. A higher dose of oxytocin was associated with a significant reduction in length of labour reported from one trial (mean difference (MD) -3.50 hours; 95% confidence interval (CI) -6.38 to -0.62; one trial, 40 women). There was a decrease in the rate of caesarean section (risk ratio (RR) 0.62; 95% CI 0.44 to 0.86 four trials, 644 women) and an increase in the rate of spontaneous vaginal birth in the high-dose group (RR 1.35; 95% CI 1.13 to 1.62, three trials, 444 women), although for both of these outcomes there were inconsistencies between studies in the size of effect. When we carried out sensitivity analysis (temporarily removing a study at high risk of bias) the differences between groups were no longer statistically significantThere were no significant differences between high- and low-dose regimens for instrumental vaginal birth, epidural analgesia, hyperstimulation, postpartum haemorrhage, chorioamnionitis or women's perceptions of experiences. For neonatal outcomes, there was no significant difference between groups for Apgar scores, umbilical cord pH, admission to special care baby unit, or neonatal mortality. The following outcomes were not evaluated in the included studies: perinatal mortality, uterine rupture, abnormal cardiotocography, women's pyrexia, dystocia and neonatal neurological morbidity.

AUTHORS' CONCLUSIONS

Higher-dose regimens of oxytocin (4 mU per minute or more) were associated with a reduction in the length of labour and in caesarean section, and an increase in spontaneous vaginal birth. However, there is insufficient evidence to recommend that high-dose regimens are advised routinely for women with delay in the first stage of labour. Further research should evaluate the effect of high-dose regimens of oxytocin for women delayed in labour and should include maternal and neonatal outcomes as well as the effects on women.

Oxytocin augmentation of labour in women with epidural analgesia for reducing operative deliveries

BACKGROUND

The rate of operative deliveries (both caesarean sections, vacuum extractions and forceps), continues to rise throughout the world. These are associated with significant maternal and neonatal morbidity. The most common reasons for operative births in nulliparous women are labour dystocia (failure to progress), and non-reassuring fetal status. Epidural analgesia has been shown to slow the progress of labour, as well as increase the rate of instrumental deliveries. However, it is unclear whether the use of oxytocin in women with epidural analgesia results in a reduction in operative deliveries, and thereby reduces both maternal and fetal morbidity.

OBJECTIVES

To determine whether augmentation of women using epidural analgesia with oxytocin will decrease the incidence of operative deliveries and thereby reduce fetal and maternal morbidity.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 June 2013).

SELECTION CRITERIA

All published and unpublished randomised and quasi-randomised trials that compared augmentation with oxytocin of women in spontaneous labour with epidural analgesia versus intent to manage expectantly were included. Cluster-randomised trials were eligible for inclusion but none were identified.Cross-over study designs were unlikely to be relevant for this intervention, and we planned to exclude them if any were identified. We did not include results that were only available in published abstracts.

DATA COLLECTION AND ANALYSIS

The two review authors independently assessed for inclusion the 16 studies identified as a result of the search strategy. Both review authors independently assessed the risk of bias for each included study. Both review authors independently extracted data. Data were checked for accuracy.

MAIN RESULTS

We included two studies, involving 319 women. There was no statistically significant difference between the two groups in either of the primary outcomes of caesarean section (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.42 to 2.12) or instrumental delivery (RR 0.88, 95% CI 0.72 to 1.08). Similarly, there were no statistically significant differences between the two groups in any of the secondary outcomes for which data were available. This included Apgar score less than seven at five minutes (RR 3.06, 0.13 to 73.33), admission to neonatal intensive care unit (RR 1.07, 95% CI 0.29 to 3.93), uterine hyperstimulation (RR 1.32, 95% CI 0.97 to 1.80) and postpartum haemorrhage (RR 0.96, 95% CI 0.58, 1.59).

AUTHORS' CONCLUSIONS

There was no statistically significant difference identified between women in spontaneous labour with epidural analgesia who were augmented with oxytocin, compared with those who received placebo. However, due to the limited number of women included in the studies, further research in the form of randomised controlled trials are required.

Oxytocin versus no treatment or delayed treatment for slow progress in the first stage of spontaneous labour

BACKGROUND

Slow progress in the first stage of spontaneous labour is associated with an increased caesarean section rate and fetal and maternal morbidity. Oxytocin has long been advocated as a treatment for slow progress in labour but it is unclear to what extent it improves the outcomes for that labour and whether it actually reduces the caesarean section rate or maternal and fetal morbidity. This review will address the use of oxytocin and whether it improves the outcomes for women who are progressing slowly in labour compared to situations where it is not used or where its administration is delayed.

OBJECTIVES

To determine if the use of oxytocin for the treatment of slow progress in the first stage of spontaneous labour is associated with a reduction in the incidence of caesarean sections, or maternal and fetal morbidity compared to situations where it is not used or where its administration is delayed.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (23 February 2013) and bibliographies of relevant papers.

SELECTION CRITERIA

Randomised controlled trials which compared oxytocin with either placebo, no treatment or delayed oxytocin in the active stage of spontaneous labour in low-risk women at term.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion, assessed risk of bias and extracted data. We sought additional information from trial authors.

MAIN RESULTS

We included eight studies in the review involving a total of 1338 low-risk women in the first stage of spontaneous labour at term. Two comparisons were made; 1) the use of oxytocin versus placebo or no treatment (three trials); 2) the early use of oxytocin versus its delayed use (five trials). There were no significant differences in the rates of caesarean section or instrumental vaginal delivery in either comparison. Early use of oxytocin resulted in an increase in uterine hyperstimulation associated with fetal heart changes. However, the early use of oxytocin versus its delayed use resulted in no significant differences in a range of neonatal and maternal outcomes. Use of early oxytocin resulted in a statistically significant reduction in the mean duration in labour of approximately two hours but did not increase the normal delivery rate. There was significant heterogeneity for this analysis and we carried out a random-effects meta-analysis; however, all of the trials are strongly in the same direction so it is reasonable to conclude that this is the true effect. We also performed a random-effects meta-analysis for the four other analyses which showed substantial heterogeneity in the review.

AUTHORS' CONCLUSIONS

For women making slow progress in spontaneous labour, treatment with oxytocin as compared with no treatment or delayed oxytocin treatment did not result in any discernable difference in the number of caesarean sections performed. In addition there were no detectable adverse effects for mother or baby. The use of oxytocin was associated with a reduction in the time to delivery of approximately two hours which might be important to some women. However, if the primary goal of this treatment is to reduce caesarean section rates, then doctors and midwives may have to look for alternative options.

A model for educational simulation of the effect of oxytocin on uterine contractions

Fetal oxygenation is sometimes compromised due to hyperstimulation of uterine contractions (UC) following labor augmentation with oxytocin. We present a model for educational simulation that incorporates the pharmacokinetic-pharmacodynamic properties of oxytocin, reproducing the effect of this drug on UC features. Six UC tracings were generated, reflecting different relevant situations. Three independent experts identified correctly the simulated situations in all tracings and attributed an average realism score of 9.4 (0-10). The model presented for simulation of the effect of oxytocin on UC provides sufficiently realistic results to be used in healthcare education and can easily be adapted to different patients and educational scenarios.

Oxytocin augmentation of labour in women with epidural analgesia for reducing operative deliveries

BACKGROUND

The rate of operative deliveries (both caesarean sections, vacuum extractions and forceps), continues to rise throughout the world. These are associated with significant maternal and neonatal morbidity. The most common reasons for operative births in nulliparous women are labour dystocia (failure to progress), and non-reassuring fetal status. Epidural analgesia has been shown to slow the progress of labour, as well as increase the rate of instrumental deliveries. However, it is unclear whether the use of oxytocin in women with epidural analgesia results in a reduction in operative deliveries, and thereby reduces both maternal and fetal morbidity.

OBJECTIVES

To determine whether augmentation of women using epidural analgesia with oxytocin will decrease the incidence of operative deliveries and thereby reduce fetal and maternal morbidity.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (29 February 2012).

SELECTION CRITERIA

All published and unpublished randomised and quasi-randomised trials that compared augmentation with oxytocin of women in spontaneous labour with epidural analgesia versus intent to manage expectantly were included. Cluster-randomised trials were eligible for inclusion but none were identified.Cross-over study designs were unlikely to be relevant for this intervention, and we planned to exclude them if any were identified. We did not include results that were only available in published abstracts.

DATA COLLECTION AND ANALYSIS

The two review authors independently assessed for inclusion the 16 studies identified as a result of the search strategy. Both review authors independently assessed the risk of bias for each included study. Both review authors independently extracted data. Data were checked for accuracy.

MAIN RESULTS

We included two studies, involving 319 women. There was no statistically significant difference between the two groups in either of the primary outcomes of caesarean section (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.42 to 2.12) or instrumental delivery (RR 0.88, 95% CI 0.72 to 1.08). Similarly, there were no statistically significant differences between the two groups in any of the secondary outcomes for which data were available. This included Apgar score less than seven at five minutes (RR 3.06, 0.13 to 73.33), admission to neonatal intensive care unit (RR 1.07, 95% CI 0.29 to 3.93), uterine hyperstimulation (RR 1.32, 95% CI 0.97 to 1.80) and postpartum haemorrhage (RR 0.96, 95% CI 0.58, 1.59).

AUTHORS' CONCLUSIONS

There was no statistically significant difference identified between women in spontaneous labour with epidural analgesia who were augmented with oxytocin, compared with those who received placebo. However, due to the limited number of women included in the studies, further research in the form of randomised controlled trials are required.

High dose versus low dose oxytocin for augmentation of delayed labour

BACKGROUND

A major cause of failure to achieve spontaneous vaginal birth is delay in labour caused by presumed inefficient uterine action. High dose may potentially increase the number of spontaneous vaginal births, but as oxytocin can cause hyperstimulation of the uterus, there is a possibility of increased adverse events.

OBJECTIVES

To compare starting dose and increment of amount of oxytocin for augmentation for women delayed in labour to determine whether augmentation by high dose of oxytocin improves labour outcomes and the effect on both maternal/neonatal outcomes and women's birth experiences.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2011) and reference lists of retrieved studies.

SELECTION CRITERIA

We included all randomised and quasi-randomised controlled trials for women in delayed in labour requiring augmentation by oxytocin comparing high starting and increment dose (defined as starting dose and increment of equal to or more than 4 mU per minute) with low dose (defined as starting dose and an increment of less than 4 mU per minute. Increase interval: between 15 and 40 minutes. The separation of low and high doses is based on an arbitrary decision.

DATA COLLECTION AND ANALYSIS

Three review authors undertook assessment of trial eligibility, risk of bias, and data extraction independently.

MAIN RESULTS

We included four studies involving 660 pregnant women. Three studies were randomised controlled trials and one trial was a quasi-randomised study. A higher dose of oxytocin was associated with a significant reduction in length of labour reported from one trial (mean difference (MD) -3.50 hours; 95% confidence interval (CI) -6.38 to -0.62; one trial, 40 women). There was a decrease in rate of caesarean section (risk ratio (RR) 0.53; 95% CI 0.38 to 0.75, four trials, 650 women) and an increase in the rate of spontaneous vaginal birth (RR 1.37; 95% CI 1.15 to 1.64, two trials, 350 women). There were no significant differences for neonatal mortality, hyperstimulation, chorioamnionitis, epidural analgesia; or neonatal outcomes of Apgar scores, umbilical cord pH or admission to special care baby unit. The following outcomes were not evaluated in the included studies: perinatal mortality, women's satisfaction, instrumental vaginal birth, uterine rupture, postpartum haemorrhage, abnormal cardiotocography, women's pyrexia, dystocia and neonatal neurological morbidity.

AUTHORS' CONCLUSIONS

Higher dose of oxytocin starting and increment dose (4 mU per minute or more) was associated with a reduction in the length of labour and in caesarean section, and an increase in spontaneous vaginal birth. However, there is insufficient evidence. The number of studies and the quality of the available evidence is of concern. Additionally, there is insufficient evidence for other maternal and neonatal outcomes, and how women feel about the higher doses of oxytocin. Therefore, no firm recommendation can be made. Further research should evaluate the effect of high dose oxytocin for women delayed in labour and should include these outcomes.

Oxytocin versus no treatment or delayed treatment for slow progress in the first stage of spontaneous labour

BACKGROUND

Slow progress in the first stage of spontaneous labour is associated with an increased caesarean section rate and fetal and maternal morbidity. Oxytocin has long been advocated as a treatment for slow progress in labour but it is unclear to what extent it improves the outcomes for that labour and whether it actually reduces the caesarean section rate or maternal and fetal morbidity. This review will address the use of oxytocin and whether it improves the outcomes for women who are progressing slowly in labour compared to situations where it is not used or where its administration is delayed.

OBJECTIVES

To determine if the use of oxytocin for the treatment of slow progress in the first stage of spontaneous labour is associated with a reduction in the incidence of caesarean sections, or maternal and fetal morbidity compared to situations where it is not used or where its administration is delayed.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 April 2011) and bibliographies of relevant papers.

SELECTION CRITERIA

Randomised controlled trials which compared oxytocin with either placebo, no treatment or delayed oxytocin in the active stage of spontaneous labour in low-risk women at term.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion, assessed risk of bias and extracted data. We sought additional information from trial authors.

MAIN RESULTS

We included eight studies in the review involving a total of 1338 low-risk women in the first stage of spontaneous labour at term. Two comparisons were made; 1) the use of oxytocin versus placebo or no treatment (three trials); 2) the early use of oxytocin versus its delayed use (five trials). There were no significant differences in the rates of caesarean section or instrumental vaginal delivery in either comparison. Early use of oxytocin resulted in an increase in uterine hyperstimulation associated with fetal heart changes. However, the early use of oxytocin versus its delayed use resulted in no significant differences in a range of neonatal and maternal outcomes. Use of early oxytocin resulted in a statistically significant reduction in the mean duration in labour of approximately two hours but did not increase the normal delivery rate. There was significant heterogeneity for this analysis and we carried out a random-effects meta-analysis; however, all of the trials are strongly in the same direction so it is reasonable to conclude that this is the true effect. We also performed a random-effects meta-analysis for the four other analyses which showed substantial heterogeneity in the review.

AUTHORS' CONCLUSIONS

For women making slow progress in spontaneous labour, treatment with oxytocin as compared with no treatment or delayed oxytocin treatment did not result in any discernable difference in the number of caesarean sections performed. In addition there were no detectable adverse effects for mother or baby. The use of oxytocin was associated with a reduction in the time to delivery of approximately two hours which might be important to some women. However, if the primary goal of this treatment is to reduce caesarean section rates, then doctors and midwives may have to look for alternative options.

Uterine activity: implications for the condition of the fetus

AIM

The aim of this review is to provide more insight in the fetal mechanisms as a response to uterine contractions and to emphasize the importance of correct assessment of uterine activity (UA) patterns during labor.

STUDY RESULTS

UA causes a decreased flow through the uterine artery. In the healthy uncompromised fetus, this will not cause fetal acidemia. The fetus has developed certain protection mechanisms to survive labor; (1) During a contraction, fetal preload increases and enables the fetus to maintain a constant blood flow through the umbilical artery and (2) UA increases the blood flow in the fetal middle cerebral artery, i.e., a brain sparing effect. The shortcoming of those protection mechanisms in the compromised fetus and in case of excessive UA increases the risk of adverse fetal outcome. The brain sparing effect will become more pronounced to compensate for the decreased umbilical artery blood flow and fetal oxygen saturation. Maintenance of normal UA, especially a sufficiently long relaxation time, is essential so that the supply of well oxygenated maternal blood to the intervillous space will be restored and the fetal cerebral oxygen saturation can remain stable.

CONCLUSION

Adequate UA monitoring is a prerequisite for proper reading and interpretation of cardiotocograms. It alarms in cases of excessive UA and can help to prevent fetal acidemia. Uterine contraction monitoring deserves full attention in daily obstetric practice.

Elevated uterine activity increases the risk of fetal acidosis at birth

OBJECTIVE

The objective of the study was to assess the role of uterine activity on fetal outcome.

STUDY DESIGN

Intrauterine pressure (IUP) recordings from consecutive term singleton, vaginal deliveries collected between June 1, 1993, and July 1, 2004, were analyzed. One thousand four hundred thirty-three recordings were included. IUP data were obtained using HP 8040A and HP M1350 cardiotocographs. For each recording the uterine contraction curve was analyzed, and the following contraction parameters were determined: relaxation time; contraction duration, frequency, amplitude, and surface; Montevideo units; and active planimeter units and contraction frequency. IUP recordings and contraction parameters from deliveries ending with an umbilical artery pH of 7.11 or less were compared with those ending with an umbilical artery pH of 7.12 or greater. Statistical analyses were performed using Student's t test and logistic regression.

RESULTS

An umbilical artery pH 7.11 or less at birth is associated with significant more uterine activity during the first and second stage of labor.

CONCLUSION

Increased uterine activity is significantly associated with a higher incidence of an umbilical artery pH of 7.11 or less.

Uterine contraction pattern as a predictor of the mode of delivery

OBJECTIVE

To determine whether analysis of the frequency or regularity of uterine contractions can distinguish between women delivering vaginally and women requiring Cesarean section for dystocia.

STUDY DESIGN

This was a case-control study. Cases meeting the following criteria were identified: nulliparous women in spontaneous labor, singleton pregnancy, cephalic presentation, 37 to 42 weeks' gestation, Cesarean section for dystocia, a minimum of three analyzable hours of electronically archived cardiotocograph (CTG) prior to onset of the second stage. Cases delivered by Cesarean section for dystocia were each matched with two controls delivering vaginally. The peak of each contraction was visually identified and electronically marked on each CTG trace. A moving average (MTIME) and standard deviation (SDTIME) of five interpeak times were calculated for successive 30-minute periods and plotted against cervical dilatation for each group.

RESULTS

Overall, both MTIME and SDTIME fell as labor progressed, with these changes being more marked in the vaginal delivery group. In women requiring oxytocin, the rate of fall of MTIME and SDTIME was significantly greater following oxytocin in the group which subsequently delivered vaginally (slope of MTIME -2.71 pre-oxytocin and -28.95 post-oxytocin, p=0.0004; slope of SDTIME -0.44 and -6.44, p=0.0002). No such change was seen in the Cesarean section group.

CONCLUSION

As normal labor progresses, there is a shortening of the intercontraction interval and an increase in contraction regularity. A successful response to oxytocin augmentation may be predicted by the change in contraction pattern following treatment.

A model for the generation of intra-uterine pressure in the human parturient uterus which demonstrates the critical role of the cervix

A mathematical model is presented which describes the relationship between intrauterine pressure and uterine wall tension. Wall tension is evaluated in terms of muscular contraction in an active myometrium and the modulating effect of a passive, compliant cervix. Using a computer programme which simulates the recruitment of contractile elements in the uterine wall, it is possible to generate theoretical pressure waveforms. The effects on these waveforms produced by changing cervical properties are demonstrated and compared with observed phenomena. The physiological and clinical implications are evaluated.

A randomized control study of oxytocin augmentation of labour. 1. Obstetric outcome

Sixty women who were progressing slowly in spontaneous labour were assigned at random to three management protocols. Group 1 were observed without the use of oxytocin for 8 h while groups 2 and 3 were managed with a low-dose and high-dose oxytocin protocol respectively. The caesarean section rates were not significantly different between the three groups: 45%, 35% and 26% respectively. Cervical dilatation rate increased significantly after oxytocin infusion in both treatment groups compared with controls. The 'delay-to-delivery' interval and second stage duration were significantly shorter in the high-dose group than in the control group. There were no measurable differences in the condition of the newborn infants between the three groups.