Objective: Fetal cells enter the maternal circulation during most pregnancies. Their persistence for years occurs in only some women and has been associated with several autoimmune diseases such as systemic sclerosis. The objective of this study was to determine whether pregnancy history influences the persistence of fetal microchimeric cells.
Methods: We reviewed all reports of studies on fetal cell microchimerism, defined as male DNA in maternal tissue, that describe individual pregnancy histories, disease diagnoses, and microchimerism status. The total numbers of pregnancies, births, and sons, the history of fetal loss (spontaneous abortion and elective termination), and the presence of a maternal autoimmune disease were tested as factors potentially associated with persistent microchimerism.
Results: One hundred twenty-four subjects from 11 studies met the inclusion criteria. Only fetal loss was significantly associated with the presence of microchimerism (odds ratio 2.4, 95% confidence interval 1.2-6.0).
Conclusion: These results suggest that fetomaternal cell trafficking following fetal loss may be important for the engraftment of microchimeric cells in maternal tissue. This may be due to an increased amount of fetomaternal transfusion or to transfer of a cell type that is more likely to engraft. We recommend that investigators in future studies on microchimerism report detailed pregnancy information, since these data are critical for the understanding of factors that influence the development of fetal cell microchimerism.