High dose versus low dose oxytocin for augmentation of delayed labour
Abstract
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 methods
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.
PICOs
Plain language summary
Oxytocin in high versus low doses for augmentation of delayed labour
Women have different lengths of labour, with first labours lasting on average eight hours (and unlikely to last more than 18 hours) and second and subsequent labours lasting an average of five hours and unlikely to last more than 12 hours. Progress in labour takes into account not just cervical dilatation, but also descent and rotation of the fetal head and the strength, duration and frequency of contractions. Some evidence suggests that up to one‐third of women in their first labour experience delay. They are often given a synthetic version of the hormone oxytocin to increase uterine contractions and shorten labour. Surprisingly for such a routine treatment, the ideal dose at which it should be given is not known, although some comparisons suggest that higher doses of oxytocin could shorten labour and reduce the chance of caesarean section with an increase in the numbers of women having a spontaneous vaginal birth compared with a lower dose. However, there are potentially harmful side effects if oxytocin causes the uterus to contract too quickly, and the baby becomes distressed. Clinicians therefore routinely adjust the dose of oxytocin to reduce the chances of the baby being distressed in labour.
From the four randomised controlled trials involving 660 pregnant women that we included in this review, results indicate that a higher dose of oxytocin (4‐7 mU per minute, compared with 1‐2 mU per minute) reduced the length of labour and the rate of caesarean sections with increased spontaneous vaginal births, but the studies did not provide enough evidence on possible differences between the high and low doses in adverse events including hyperstimulation of the uterus and outcomes for the newborn infant. No trial reported on how the women experienced the births. The overall quality of the included trials was not good, but this might reflect how the clinical trials were reported.
While the evidence we have showed that the high doses reduced the length of labour and the rate of caesarean sections, the number and quality of the studies is of concern and not enough is known about the effect on the baby or women's birth experiences for the higher dose oxytocin to be recommended as treatment for women delayed in labour. We recommend that more research is carried out.
