Sample size calculation
The sample size was calculated using the comparison of drain output during the first eight postoperative hours between women on Warfarin therapy undergoing Cesarean delivery treated with local application of tranexamic acid-impregnated gelatin sponge (G1) and those treated with the application of gelatin sponge alone (G2) compared to non-treated matched women (G3). As reported in a previous publication on spine surgery by Liang et al. [