Figure 3.

Graph of maternal-fetal cell transfer and presence during pregnancy

(A–C)During pregnancy, fetal cell trafficking to the mother starts at 10–12 days gestation in rodents, at 4 weeks in Rhesus monkey and at 4–6 weeks in humans. As the pregnancy advances there is a significant increase, reaching its maximum value at delivery at 21 days gestation in rodents (A), at 24 weeks in Rhesus monkey (B), and 36 weeks in humans (C). The chimeric cells remain up to 42 days in the maternal body in rodents, not known in Rhesus monkey and up to 27 years in humans. The types of cells being transferred from fetus to mother are stem cells and differentiated cells. The degree of cell differentiation could determine its function, being stem cells responsible for tissue repair and regeneration, and differentiated cells triggering maternal and fetal immune responses (Fujiki et al., 2008).