The placenta was once thought of as a wall between mother and baby. It turns out to be more like a two-way border crossing, and some of the travelers stay for life. What Is Microchimerism? Microchimerism is the presence of a small number of cells from another genetically distinct individual inside a person's body. The most common source is pregnancy. During gestation, … [Read more...] about Your Mother’s Cells May Still Be Living in Your Body — Science Calls It Microchimerism