Influence of birth order on overall survival and GVHD incidence. (A) Overall survival and GVHD incidence in recipients with a YSD (n = 168) compared with recipients with an OSD (n = 143) are not statistically significantly different. (B) Female donors with female recipients have a higher non-GVHD death incidence (ie, relapse) in YSD compared with OSD (hazard ratio = 3.76, P = .094). (C) Adult YSD are subdivided by gender. Female donors in female recipients have a significantly (P = .008) reduced GVHD incidence compared with M→M.