Summary: Women Who Bear Children Have a Reduced Risk of Developing Breast Cancer

The ability of cells from a developing fetus to cross the placenta and take up long-term residence within its mother is called fetal microchimerism. While fetal microchimerism has been shown to be a mechanism to explain autoimmune disease, it may also benefit mothers by putting her immune system on alert to destroy malignant cells.

• In a recent study conducted at the University of Washington and Fred Hutchinson Cancer Research Center, researchers studied 82 women (35 of whom had been previously diagnosed with breast cancer). Approximately two-thirds of the women studied had had children, and more than half of the participants had given birth to at least one son. The researchers took blood samples from each participant and searched them for male DNA, as they reasoned it is a relatively definitive matter to detect the male Y chromosome among the mother’s female cells within a blood sample. Among the women with breast cancer, only five had male DNA in their bloodstream. Three of the five had previously given birth to sons, one had previously had an abortion and the other had never been knowingly pregnant. In all, about 14% of all the women in the breast cancer group had male DNA in their bloodstream compared to 43% of women in the non-breast cancer group. According to Dr. Vijayakrishna K. Gadi, assistant professor at the University of Washington and research associate at the Fred Hutchinson Cancer Research Center, the research in this study found that “these persisting fetal cells may be giving women an edge against developing breast cancer.” The ability of cells from a developing fetus to cross the placenta and take up long-term residence within its mother is called fetal microchimerism. According to the researchers in this study, while fetal microchimerism has been shown to be a mechanism to explain autoimmune disease, it may also benefit mothers by putting her immune system on alert to destroy malignant cells. According to Dr. Gadi, these findings could provide a starting point for future research on the role of fetal microchimerism in the prevention of cancer.

¹Fetal Microchimerism in Women with Breast Cancer, Cancer Research, October 1, 2007, pp. 9035-9038.