Comparison 3. Trials on mastectomy and axillary surgery.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Incidence of postoperative seroma	7	496	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.72, 1.51]
3.2 Mean volume of seroma	3	193	Std. Mean Difference (IV, Random, 95% CI)	‐1.06 [‐3.23, 1.11]
3.3 Total volume of drained seroma	3	258	Std. Mean Difference (IV, Random, 95% CI)	‐0.54 [‐1.06, ‐0.02]
3.4 Number of days for persistent drainage	3	195	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.68 [‐0.98, ‐0.39]
3.5 Surgical site infection	5	364	Risk Ratio (M‐H, Fixed, 95% CI)	1.18 [0.44, 3.16]
3.6 Postoperative complications	5	417	Risk Ratio (M‐H, Fixed, 95% CI)	0.95 [0.39, 2.28]
3.7 Length of hospital stay	2	195	Std. Mean Difference (IV, Fixed, 95% CI)	‐0.93 [‐1.23, ‐0.62]