Bidirectional transplacental exchange characterizes human pregnancy. Cells exchanged
between mother and fetus can durably persist as microchimerism and may have both short-
and long-term consequences for the recipient. The amount, type, and persistence of
microchimerism are influenced by obstetric characteristics, pregnancy complications,
exposures to infection, and other factors. A reproductive-aged woman enters pregnancy
harboring previously acquired microchimeric “grafts,” which may influence her …