Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Adverse effects
Systematic review	140 women 2 RCTs in this analysis	Proportion of women who had a premature birth 5/70 (7%) with low-dose aspirin alone (75–81 mg/day) 11/70 (16%) with low-dose aspirin plus unfractionated heparin (5000 U twice daily)	RR 0.5 95% CI 0.2 to 1.3 This analysis was likely to have been underpowered to detect clinically important differences between groups		Not significant
Systematic review	140 women 2 RCTs in this analysis	Proportion of women who had fetal growth restriction 2/70 (3%) with low-dose aspirin alone (75–81 mg/day) 6/70 (9%) with low-dose aspirin plus unfractionated heparin (5000 U twice daily)	RR 0.3 95% CI 0.1 to 1.6 This analysis was likely to have been underpowered to detect clinically important differences between groups		Not significant
RCT	72 women	Adverse effects with low-dose aspirin alone (80 mg/day) with low-dose aspirin plus unfractionated heparin (5000 U twice daily) Absolute numbers not reported	Significance not assessed The trial reported that it was randomised, but the method of randomisation was not described. The level of blinding was not reported