The use of parenteral opioid medications may be supported for effective pain relief during labor, according to a Cochrane Database Systematic Review. However, the evidence supporting this notion was deemed to be low- to very-low quality.
Investigators reviewed 61 studies obtained from the Cochrane Pregnancy and Childbirth Trials Register, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform. Studies included randomized controlled trials that assessed the use of intramuscular or intravenous opioids in women undergoing labor, as well as studies in which opioids were compared with placebo, no treatment, another opioid, inhaled analgesia, and non-pharmacologic interventions.
Treatment satisfaction was comparable in mothers during labor in a study in which 50 mg or 100 mg intramuscular pethidine was compared with placebo (risk ratio (RR), 7.00; 95% CI, 0.38-128.87; very low-quality evidence). In addition, there were no differences between treatment and placebo in the number of women who requested an epidural in this study (RR, 0.50; 95% CI, 0.14-1.78; very low-quality evidence).
Another trial indicated that pethidine achieved overall pain reduction (RR, 25; 95% CI, 1.56-400; low quality evidence) as well as pain reduction during labor (RR, 1.75; 95% CI, 1.24-2.47), as measured by a reduction in the visual analogue scale score ≥40 mm. Fewer women required additional analgesia in 1 smaller trial after receiving an opioid (RR, 0.71; 95% CI, 0.54-0.94). Few data were available to suggest a harmful impact of opioids on the mother or baby; however, opioids were consistently shown to be associated with maternal nausea, drowsiness, and vomiting.
A limitation of this review was the inclusion of studies that were predominantly not blinded, resulting in downgrading of evidence quality.
The investigators note that further research may be necessary “to determine which analgesic intervention is most effective, and provides greatest satisfaction to women with acceptable adverse effects for mothers and their newborn[s].”
Smith LA, Burns E, Cuthbert A. Parenteral opioids for maternal pain management in labour [published online June 5, 2018]. Cochrane Database Syst Rev. doi:10.1002/14651858.CD007396.pub3