Cells that are not our own may unlock secrets about our health

During pregnancy, maternal and fetal cells migrate back and forth across the placenta, with fetal cells entering the mother's bloodstream and tissues. They can settle in maternal organs such as the thyroid, liver, lungs, brain and heart—and can persist there for decades. Conversely, maternal cells can enter the fetus and be passed down to future generations, essentially creating a lifelong connection between mothers, their offspring and their descendants.