Abstract: We have included 18 studies (involving 1498 women) in this review. However, only nine of the included studies (with 750 women) reported 24 comparisons of analgesia with other analgesia or placebo and had data that could be included in our meta-analyses. The majority of studies investigated pharmacological analgesics and these were grouped into classes for this review. Non-steroidal anti-inflammatory drugs (NSAIDs) were significantly better than placebo at relieving pain from uterine involution as assessed by their summed pain intensity differences (SPID) (mean difference (MD) 4.34; 95% confidence interval (CI) 2.87 to 5.82; three studies, 204 women) and summed pain relief scores (MD 5.94; 95% CI 3.83 to 8.01; three studies, 204 women). NSAIDS were compared with opioids in one small study of 23 women reporting SPID and summed pain relief and found no difference. A larger study of 127 women found NSAIDs to be significantly better than opioids at reducing pain intensity six hours following study intervention (MD -0.70; 95% CI -1.04 to -0.35). Opioids were compared with placebo in three studies that could be included in meta-analyses; one small study of 23 women reporting SPID and summed pain relief and found no difference. One study of 95 women found no difference in pain intensity six hours following the study intervention. A third study of 108 women found significantly more women in the placebo group reported no pain relief than women in the opioid group (risk ratio 0.10; 95% CI 0.04 to 0.23). Aspirin was significantly better than paracetamol when pain intensity score was assessed six hours after study intervention (MD 0.85; 95% CI 0.29 to 1.41; one study 48 women) at relieving pain from uterine involution. Paracetamol was not better than placebo when pain intensity was assessed six hours after the study intervention in one study of 48 women. Non-steroidal anti-inflammatory drugs (NSAID) including aspirin were better than placebo at relieving pain from uterine cramping/involution following vaginal birth. NSAIDs were better than paracetamol and paracetamol was not better than placebo, though numbers of participants for these comparisons were small. Data for opioids compared with NSAIDs and opioids compared with placebo were conflicting, with some measures showing similar effect and others indicating NSAIDs were better than opioids and opioids were not better than placebo. There were insufficient data to make conclusions regarding the effectiveness of opioids at relieving pain from uterine cramping/involution. The median year of publication of included studies was 1981; therefore more research is needed to assess the effectiveness of current pharmacological and non-pharmacological analgesia at relieving pain from uterine cramping/involution following vaginal birth.

Plain-language summary: Types of analgesia used to relieve the pain include paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs) included aspirin and naproxen, opioids including codeine and non-pharmacological methods such as transcutaneous electrical nerve stimulation (TENS). The results from 18 randomised controlled trials involving 1498 women, of which nine (750 women) had data that could be included in the review meta-analyses, indicated that aspirin and other NSAIDs including naproxen were more effective at relieving uterine cramping pain than paracetamol or a placebo. NSAIDs included naproxen, aspirin, ketorolac and flurbiprofen. Only naproxen is still used in women who are breastfeeding. Aspirin is not recommended for use by breastfeeding women as there is concern that it will be passed to the baby in the breast milk. Codeine was not always more effective than a placebo or NSAIDs in the included studies and can sedate breastfed babies. Women offered codeine for pain relief should be informed about the potential for adverse effects for their babies. Codeine should only be prescribed for breastfeeding women with after birth pain if there is no alternative and their breastfed infants should be closely monitored for sedation and signs of codeine toxicity. Information about the safety of the NSAIDs for breastfeeding women and their babies was limited. The majority of analyses in this review included only one study with small numbers of participants. The average year of the included studies is 1981 and therefore further research is recommended comparing NSAIDs currently available and known to be safe for women who are breastfeeding and their babies.