Parenteral opioids for maternal pain management in labour

Background Parenteral opioids (intramuscular and intravenous drugs including patient‐controlled analgesia) are used for pain relief in labour in many countries throughout the world. This review is an update of a review first published in 2010. Objectives To assess the effectiveness, safety and acceptability to women of different types, doses and modes of administration of parenteral opioid analgesia in labour. A second objective is to assess the effects of opioids in labour on the baby in terms of safety, condition at birth and early feeding. Search methods We searched Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (11 May 2017) and reference lists of retrieved studies. Selection criteria We included randomised controlled trials examining the use of intramuscular or intravenous opioids (including patient‐controlled analgesia) for women in labour. Cluster‐randomised trials were also eligible for inclusion, although none were identified. We did not include quasi‐randomised trials. We looked at studies comparing an opioid with another opioid, placebo, no treatment, other non‐pharmacological interventions (transcutaneous electrical nerve stimulation (TENS)) or inhaled analgesia. Data collection and analysis Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of each evidence synthesis using the GRADE approach. Main results We included 70 studies that compared an opioid with placebo or no treatment, another opioid administered intramuscularly or intravenously or compared with TENS applied to the back. Sixty‐one studies involving more than 8000 women contributed data to the review and these studies reported on 34 different comparisons; for many comparisons and outcomes only one study contributed data. All of the studies were conducted in hospital settings, on healthy women with uncomplicated pregnancies at 37 to 42 weeks' gestation. We excluded studies focusing on women with pre‐eclampsia or pre‐existing conditions or with a compromised fetus. Overall, the evidence was graded as low‐ or very low‐quality regarding the analgesic effect of opioids and satisfaction with analgesia; evidence was downgraded because of study design limitations, and many of the studies were underpowered to detect differences between groups and so effect estimates were imprecise. Due to the large number