High dose versus low dose oxytocin for augmentation of delayed labour

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.

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.

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

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.

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

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.

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.