LBR OHSS rate OR 1.39; 95% CI 0.81 to 2.40 OR 0.29; 95% CI 0.18 to 0.49 Tso et al 2014 Metformin Metformin Miscarriage Rate COCs OR 0.50, 95% CI 0.30–0.83, P = 0.010 WMD –1.11, 95% CI –1.86 to –0.36, P = 0.004 Palomba et al. 2012 112 Page 108 of 258