Influence of pretransplant pregnancy on survival of renal allografts from living donors

Background. The presence of a small number of cells of donor origin in orga n transplant recipients (microchimerism) may influence allograft; survival and may induce tolerance. Postpartum women may be microchimeric to offsprin g hematopoietic. cells up to 27 years. We hypothesized that mothers receivi ng renal allografts from offspring would have better graft survival compare d with either fathers receiving allografts from offspring, or mothers recei ving allografts from nonoffspring donors. Methods. We analyzed 1803 living related kidney transplants from the UNOS d atabase performed between January 1, 1990, and December 31, 1995, for mothe rs and fathers who received grafts from offspring with one haplotype match. We also compared these mothers with parous females receiving a kidney from nonoffspring donors (spouse and other biologically related or unrelated fa mily members). A multivariate logistic regression method was used to analyz e the effect of donor type, as well as other recipient, donor, and transpla nt characteristics, on graft and patient survival. Results. Mothers receiving one haplotype-matched offspring renal allografts did not have better graft survival at I or 3 years posttransplant compared with fathers receiving similar grafts. There was also no difference in gra ft or patient survival between mothers receiving kidney grafts from either offspring or nonoffspring donors. Graft survival in mothers with multiple p regnancies was poorer than those with a single pregnancy. Conclusions. It is possible that persistent microchimerism of fetal cells i n maternal circulation may, for some mothers, cause a detectable improvemen t in graft or patient survival. Comparison of female and male recipients fr om the UNOS database did not reveal any differences in outcomes. If mothers are tolerant to their offspring, our results indicate that this microchime rism may not improve renal allograft or patient survival in offspring donor to maternal recipient combinations. Lastly, more sensitive pretransplant c ross-match assays may need to be implemented in multiparous women, given ou r results.