DNA, sex and women

I recently read a story on the social media to the effect that research has shown that women retain DNA from every man they have slept with.

The reason given was that cells from a man’s sperm become integrated into the woman’s body after every sexual experience. How true is this?
Michael (by SMS)

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This is another false information which has recently gone viral on the social media courtesy of a website noted for creating false medical information. In reality, the story is based on a study first published in PLOS ONE in 2012, by lead author William F. N. Chan, a biochemist at the University of Alberta. The actual research was based on the discovery of some amount of male DNA in the brain of some dead women at autopsy, a term known as ‘Micro-chimerism’ in medical parlance. Micro-chimerism is said to be possible from prior pregnancies, recognised or vanished male twin, an older male sibling or non irradiated blood transfusion but never from sex as the information in question has wrongly interpreted. This however does not discountenance the need to avoid having sex with multiple partners because of its negative effects on the body.