Microchimerism is the presence of cells from one individual in another
genetically distinct individual. Pregnancy is the main cause of natural
microchimerism through transplacental bidirectional cell trafficking between
mother and fetus. The consequences of pregnancy-related microchimerism are under
active investigation. However, many authors have suggested a close relationship
linking fetal microchimerism and the development of autoimmune diseases. It has
been more than ten years now since the demonstration of the presence of a
significant high number of fetal microchimeric cells residing in thyroid glands
from operated patients with Graves' disease. This intrathyroidal fetal
microchimerism is an attractive candidate mechanism for the modulation of Graves'
disease in pregnancy and the postpartum period
