Comparison 2. Aspirin versus placebo or usual care.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Pregnancy loss	3	71	Risk Ratio (M‐H, Random, 95% CI)	1.05 [0.66, 1.68]
2 Premature delivery	1	40	Risk Ratio (M‐H, Random, 95% CI)	5.0 [0.26, 98.00]
3 Adverse pregnancy outcome (pregnancy loss or preterm labour)	1	40	Risk Ratio (M‐H, Random, 95% CI)	2.0 [0.58, 6.91]
4 IUGR with interventions	3	125	Risk Ratio (M‐H, Random, 95% CI)	0.55 [0.17, 1.72]
5 Adverse pregnancy outcome (pregnancy loss or IUGR)	3	125	Risk Ratio (M‐H, Random, 95% CI)	0.90 [0.55, 1.49]
6 Neonatal intensive care admission	1	40	Risk Ratio (M‐H, Random, 95% CI)	1.0 [0.16, 6.42]
7 Caesarean section	2	106	Risk Ratio (M‐H, Random, 95% CI)	1.11 [0.47, 2.61]
8 Weighted mean difference for birthweight	2	106	Mean Difference (IV, Random, 95% CI)	177.39 [‐66.59, 421.36]