Comparison 1. Prevention of upper gastrointestinal bleeding.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 All cause mortality to near term age or discharge	1	53	Risk Ratio (M‐H, Fixed, 95% CI)	2.42 [0.70, 8.38]
1.1 H2RA versus no treatment	1	53	Risk Ratio (M‐H, Fixed, 95% CI)	2.42 [0.70, 8.38]
2 Any upper gastrointestinal bleeding in infants at risk of upper gastrointestinal bleeding	4	329	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.22, 0.58]
2.1 H2RA versus no treatment	4	329	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.22, 0.58]
3 Gastric lesions detected by endoscopy and macroscopically	1	48	Risk Ratio (M‐H, Fixed, 95% CI)	0.49 [0.28, 0.84]
3.1 H2RA versus no treatment	1	48	Risk Ratio (M‐H, Fixed, 95% CI)	0.49 [0.28, 0.84]
4 Serious adverse reactions	4	329	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4.1 H2RA versus no treatment	4	329	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]