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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.