Olufemi T Oladapo, Babasola O Okusanya, Edgardo Abalos

There is general agreement that oxytocin given either through the intramuscular or intravenous route is effective in reducing postpartum blood loss. However, it is unclear whether the subtle differences between the mode of action of these routes have any effect on maternal and infant outcomes. This is an update of a review first published in 2012. To determine the comparative effectiveness and safety of oxytocin administered intramuscularly or intravenously for prophylactic management of the third stage of labour after vaginal birth. We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (7 September 2017) and reference lists of retrieved studies. Randomised trials comparing intramuscular with intravenous oxytocin for prophylactic management of the third stage of labour after vaginal birth. We excluded quasi-randomised trials. Two review authors independently assessed studies for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of the evidence using the GRADE approach. Three studies with 1306 women are included in the review and compared intramuscular versus intravenous oxytocin administered just after the birth of the anterior shoulder or soon after the birth of the baby. Studies were carried out in hospital settings in Turkey and Thailand and recruited women with singleton, term pregnancies. Overall, the included studies were at moderate risk of bias: none of the studies provided clear information on allocation concealment or attempted to blind staff or women. For GRADE outcomes the quality of the evidence was very low, with downgrading due to study design limitations and imprecision of effect estimates.Only one study reported severe postpartum haemorrhage (blood loss 1000 mL or more) and showed no clear difference between the intramuscular and intravenous oxytocin groups (risk ratio (RR) 0.11, 95% confidence interval (CI) 0.01 to 2.04; 256 women; very low-quality evidence). No woman required hysterectomy in either group in one study (no estimable data, very low-quality evidence), and in another study one woman in each group received a blood transfusion (RR 1.00, 95% CI 0.06 to 15.82; 256 women; very low-quality evidence). Other important outcomes (maternal death, hypotension, maternal dissatisfaction with the intervention and neonatal jaundice) were not reported by any of the included studies. There were no clear differences between groups for other prespecified secondary outcomes reported (postpartum haemorrhage 500 mL or more, use of additional uterotonics, retained placenta or manual removal of the placenta). Very low-quality evidence indicates no clear difference between the comparative benefits and risks of intramuscular and intravenous oxytocin when given to prevent excessive blood loss after vaginal birth. Appropriately designed randomised trials with adequate sample sizes are needed to assess whether the route of prophylactic oxytocin after vaginal birth affects maternal or infant outcomes. Such studies could be large enough to detect clinically important differences in major side effects that have been reported in observational studies and should also consider the acceptability of the intervention to mothers and providers as important outcomes.