The effect of two groups of intrathecal fentanyl doses on analgesic outcomes and adverse effects in parturients undergoing cesarean delivery: a systematic review and meta-analysis of randomized controlled trials with trial sequential analysis

•Variable doses of intrathecal fentanyl for peri-operative analgesia at cesarean.•Meta-analysis of randomized controlled trials comparing ≤12.5 μg and >12.5 μg.•Higher doses result in reduced intra-operative analgesic supplementation.•Higher doses associated with prolonged time to first analgesia.•Higher doses associated with more maternal pruritus.