Change in Hematocrit as a function of donor-recipient gender pair. Donor-recipient pairs: FM, female donor male recipient; MM, male donor male recipient; FF, female donor female recipient; MF male donor female recipient. Pair 1 − Pair 2 = ΔHct for pair 1 − ΔHct for pair 2. , Bonferroni-corrected value = 0.05/4 groups = 0.0125. All comparisons in which the recipient genders were discordant were significant statistically. By contrast, comparisons in which the recipient genders were identical were not significant statistically.