Comparison 2. Subgroup analysis by prospective registration.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 30‐Day mortality	31	16729	Risk Ratio (M‐H, Random, 95% CI)	0.99 [0.86, 1.15]
2.1.1 Prospectively registered trials	18	12932	Risk Ratio (M‐H, Random, 95% CI)	1.08 [0.89, 1.31]
2.1.2 Trials without prospective registration	13	3797	Risk Ratio (M‐H, Random, 95% CI)	0.81 [0.66, 1.00]