Interim Staff Scientists believe that the passing of stem cells from an unborn baby into the mother’s bone marrow during the early stages of pregnancy may be the secret to why women live longer than men. A study, published in a recent edition of The Lancet medical journal, suggests that the stem cells of an unborn baby could benefit the mother by replacing ageing cells, repairing damage and fighting disease. The infusion of cells could also explain why women who have had children are less likely to develop arthritis, multiple sclerosis and breast cancer. Professor Nick Fist, a specialist in fetal medicine at Queen Charlotte’s Hospital who led the research, explained that the researchers found stem cells from the fetus are stored in the mother’s bone marrow and can even turn to bone, staying with the woman for the rest of her life. “Every time a woman gets pregnant, she gets a shower of stem cells that can fight disease,” he said.