Pregnancy can be a little creepy.

Son's DNA found inside mother's brain

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.

During a pregnancy, cells from mother and fetus can cross the placenta and survive for decades in the skin, liver and s... – a phenomenon called fetal microchimerism.

Fetal DNA can also cross the blood-brain barrier and enter the brain ...

... autopsied 59 brains of deceased women... They amplified the DNA that they found, creating many more copies, and looked for the presence of a male Y chromosome.

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.