Methods	RCT 2-arm parallel group design.
Participants	Italy: hospital care setting. 40 women. Full-term pregnancy, cx ≥ 4 cm, in spontaneous active labour and requiring analgesia
Interventions	Experimental: IM tramadol 100 mg (N = 20). Control: IM pethidine 75 mg (N = 20).
Outcomes	Primary outcome: maternal pain relief and acceptability. Pain assessed hrly up to 5 hrs, VAS 1-3 Secondary outcomes: maternal: observations (pulse, BP, respiratory rate, arterial oxygen saturation). Neonatal: Apgar at 1 and 5 min. Umbilcal cord pH
Notes	Second dose of study drug allowed after 2 hrs as required. Italian language, translation obtained. Data were presented in a way in which we were not able to incorporate them into data tables in RevMan
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer generated.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Blinding (performance bias and detection bias) Women	Unclear risk	Not reported.
Blinding (performance bias and detection bias) Clinical staff	Unclear risk	Not reported.
Blinding (performance bias and detection bias) Outcome assessor	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear how many women analysed as only percentages reported
Selective reporting (reporting bias)	Unclear risk	Unclear.
Other bias	High risk	No baseline characteristics table - unclear re maternal parity Likely response bias as no information on whom women reported to about their pain post injection