Table 3.

Characteristics and review of studies.

Study or subgroup	Prophylaxis used		Prophylaxis not used		Weight	Relative risk H-M, Random, 95% CI
	Events	Total	Events	Total
Allende et al. (2015)	12	409	19	384	21.7%	0.59 (0.29; 1.21)
Baratz et al. (2015)	27	3434	33	3080	42.6%	0.73 (0.44, 1.22)
Hacek et al. (2008)	11	912	14	583	17.8%	0.50 (0.23; 1.10)
Rao et al. (2008)	9	636	20	741	18%	0.53 (0.24; 1.14)
Total (95% CI)	59	5391	86	4788	100%	0.62 (0.44; 0.86)

Heterogeneity: tau² = 0.0; chi² = 0.9; df = 3 (p = 0.83); I² = 0%.

Overall test effect: Z = 2.87 (p = 0.004).