Armson 1992.

Methods	2‐centre RCT.
Participants	15 women. Inclusion criteria: in preterm labour. Gestational age range: between 27‐36 weeks' gestation. Exclusion criteria: women with obstetric or medical contraindications to tocolysis. Setting: Pennsylvania, USA (timeframe not stated).
Interventions	MAGNESIUM VS BETAMIMETICS 1) magnesium sulphate (n = 8): loading dose 6 g IV MgSO4 over 30 minutes. Maintenance at 2 g/hr. Increased by 0.5 g/hr every 30 minutes until tocolysis achieved, a maximum of 4 g/hr attained or unacceptable side effects; 2) ritodrine (n = 7): loading dose 50 μg/min. Maintenance: increased by 50 μg/min at 15 minute intervals until tocolysis attained, a maximum of 350 μg/min, or unacceptable side effects. Duration: if tocolysis was successful the infusion rate was maintained at the lowest effective dose for 12 hrs.
Outcomes	Fetal and maternal deaths, birth within 12 hrs, and maternal cardiovascular and respiratory effects.
Notes	Antenatal corticosteroid use: 'were not given'. Surfactant use: not stated. Sample‐size calculation: not stated. Funding: not stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"patients were prospectively randomised with a random number table."
Allocation concealment (selection bias)	Unclear risk	No details provided.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No details provided, but blinding unlikely due to the nature of the intervention.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details provided.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Women were excluded if they progressed to preterm birth in spite of maximum therapy or who had adverse side effects necessitating discontinuation of therapy. 1 woman treated with MgSO4 progressed to birth in spite of maximum therapy and was therefore excluded from the study.
Selective reporting (reporting bias)	Unclear risk	Not all expected outcomes were reported.
Other bias	Low risk	No apparent evidence of other bias.