A Pregnancy Souvenir: Cells That Are Not Your Own
They collected tissue from 26 women who had died during or just after pregnancy. All of them had been carrying sons. The pathologists then stained the samples to check for Y chromosomes.
Essentially, the scientists were looking for male cells in female bodies. And their search was stunningly successful.
As reported last month in the journal Molecular Human Reproduction, the researchers found cells with Y chromosomes in every tissue sample they examined. These male cells were certainly uncommon — at their most abundant, they only made up about one in every 1,000 cells. But male cells were present in every organ that the scientists studied: brains, hearts, kidneys and others. In a 2012 study, Dr. Nelson and her colleagues examined the brains of 59 deceased older women and found Y chromosomes in 63 percent of them. (Many studies on fetal microchimerism focus on the cells left behind by sons, because they are easier to distinguish from the cells of their mother).