No doubt, mothers always have their children in the back of their minds – now it seems that this is quite literally true. Fetal DNA can enter a mother’s brain and remain there for decades, according to autopsies of female brains. While, during a pregnancy, cells from mother and fetus can cross the placenta and survive for decades in the skin, liver and spleen – a phenomenon called fetal microchimerism.
In this regard, fetal DNA can also cross the blood-brain barrier and enter the brain of pregnant mice. But it’s unclear whether the same happens in humans, says Lee Nelson of the Fred Hutchinson Cancer Research Center in Seattle. If it does, having foreign DNA in your brain may be one possible explanation for why certain neurological disorders, such as Alzheimer’s disease, are more common in women who have had children (European Journal of Neurology, doi.org/dwwz99). To investigate this, Nelson and her colleagues autopsied 59 brains of deceased women – 33 of whom had Alzheimer’s disease. They amplified the DNA that they found, creating many more copies, and looked for the presence of a male Y chromosome.
However, they found it in 63 per cent of the brains. This male DNA showed up in many different brain regions and some of it had been there for a very long time: one brain that contained the male DNA was from a 94-year-old woman.