Methods	RCT, 2-arm parallel group design.
Participants	Setting: UK - hospital. 205 women. Healthy women 38-41 weeks’ gestation, uncomplicated pregnancy, spontaneous or induced labour onset, in active labour and requiring analgesia. Excluded if epidural or forceps birth likely Parity: mixed.
Interventions	Experimental: IM meptazinol 100 mg (N = 98). Control: IM pethidine 100 mg (N = 99). Additional doses of test drug allowed at intervals no less than 2 hrs if required to a maximum of 3 doses. All women could receive nitrous oxide if required and prochlorperazine 12.5 mg IM for nausea and vomiting. Epidural at midwife discretion
Outcomes	Maternal outcomes: pain intensity 30 min and then hourly intervals until birth (rated none, mild, moderate, severe), pain relief (rated none, slight, moderate, strong or complete), type of birth, additional analgesia required, nausea and vomiting. Neonatal outcomes: Apgar at 1 and 5 min, resuscitation. Within 72 hrs postpartum feeding problems, irritability and muscle tone
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported.
Allocation concealment (selection bias)	Low risk	Coded ampoules kept at a site remote from trial.
Blinding (performance bias and detection bias) Women	Low risk	Described as double blind, used coded ampoules and states that identity of drug unknown
Blinding (performance bias and detection bias) Clinical staff	Low risk	Described as double blind, used coded ampoules and states that identity of drug unknown
Blinding (performance bias and detection bias) Outcome assessor	Low risk	Blind outcome assessor for all bar 15% of women.
Incomplete outcome data (attrition bias) All outcomes	Low risk	8 women excluded from analysis as delivered within 30 minutes of administration
Selective reporting (reporting bias)	Unclear risk	Unclear.
Other bias	Unclear risk	Balanced at baseline for age and weight, but imbalance in parity. 43/98 multip meptazinol group versus 34/99 in pethidine group