Intrathecal morphine versus fascial plane blocks after caesarean delivery: An updated meta-analysis with trial sequential analysis

Intrathecal morphine (ITM) provides prolonged analgesia after caesarean delivery but causes opioid-related adverse effects. Fascial plane blocks (FPBs) may be an alternative, although their comparative efficacy remains uncertain.

We systematically searched the Cochrane Central Register of Controlled Trials (CENTRAL), Embase, PubMed, Web of Science, and Scopus (from inception to 24 July 2026) for randomised controlled trials comparing ITM with FPBs. The primary outcome was 24-h opioid consumption in intravenous morphine milligram equivalents (IV-MME).

Twenty-six trials were included. Fifteen trials involving 1250 participants reported 24-h opioid consumption. ITM produced a small reduction compared with FPBs (mean difference - 3.16 mg IV-MME, 95% confidence interval - 6.30 to - 0.02; p = 0.049; I2 = 96.1%). The prediction interval crossed the null, Egger's test indicated funnel plot asymmetry, and the trim-and-fill sensitivity analysis produced a non-significant estimate in the opposite direction. These findings are difficult to interpret in the presence of substantial heterogeneity. TSA showed that the accrued information size was sufficient. Pain scores were similar, with small differences favouring ITM at isolated time points. ITM increased postoperative nausea and vomiting (risk ratio 1.87), pruritus (1.65), urinary retention (3.89), and respiratory depression (2.60). The trim-and-fill estimate for pruritus was not statistically significant, although this finding should also be interpreted cautiously. Effects differed by FPB technique but not by ITM dose. The certainty of evidence ranged from moderate to very low.

The comparative effects of ITM and FPBs varied by block technique, and the findings do not support routine replacement of ITM with FPBs. Selected FPBs may be considered when ITM is not administered, with the choice guided by technique-specific evidence, patient preferences, and the additional procedural time, expertise, and resources required.