Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table
Allocation concealment (selection bias)	Low risk	Numbered, sealed envelopes
Blinding of participants and personnel (performance bias)	High risk	Unlikely
Blinding of outcome assessment (detection bias)	Unclear risk	Not reported
Incomplete outcome data (attrition bias)	Low risk	Six women withdrawn from participation. One failed epidural converted to GA. No serious maternal or fetal complications attributable to any of the three anaesthetic methods. 84 live‐born infants and no neonatal deaths
Selective reporting (reporting bias)	Unclear risk	Unclear whether intention‐to‐treat
Other bias	Low risk	Groups well balanced for race, percentages of nulliparous women, blood pressures in labor. Higher birth weights for combined spinal‐epidural group