“…Risk of bias for included studies is presented in a summary table ( Figure S1). We included 15 RCTs comparing CC with letrozole (1957 women, 3892 cycles) [23][24][25][27][28][29]33,[38][39][40][41]44,46,51,54 , two RCTs comparing CC with anastrozole (329 women, 329 cycles) 52,53 , two RCTs comparing CC with CC plus metformin (101 women, 140 cycles) 35,42 , three RCTs comparing CC with tamoxifen (571 women, 844 cycles) 26,38,54 , three RCTs comparing CC with CC plus N-acetyl cysteine (NAC; 340 women, 300 cycles) 35,43,49 and two RCTs comparing CC with CC plus isosorbide mononitrate (ISMN) as nitric oxide (NO) donor (120 women, 304 cycles) 30,36 .…”