No evidence that sex leads to male DNA in women’s brains

A Facebook post claims every time a woman has sex with a man, she retains some of his “living DNA”.

“This bombshell discovery has been unearthed during a brand-new study by the University of Seattle and the Fred Hutchinson Cancer Research Center,” it says.

The discovery was accidental, the post notes. “Scientists were initially attempting to identify whether ladies who were pregnant with a son are more susceptible to specific neurological illnesses that take place more regularly in males.”

Male DNA in the female brain

The claim is made on a number of posts and videos shared on Facebook and Twitter in Kenya and elsewhere. Many claim the male DNA is found in women’s brains.

And an article on the Deccan Chronicle says: “Scientists say there are only four ways male DNA cells are likely show up in the female brain: unknown abortion, possibly a vanished male twin, older brother transferred by the maternal circulation and sexual intercourse.”

Does sex cause male DNA to lodge in women’s brains? We checked.

Study of ‘male microchimerism’

Africa Check asked the US-based Fred Hutchinson Cancer Research Centre (FHCRC), which is often cited as evidence, about the claims. Spokesperson Natalie Myers responded that “there is no evidence the DNA is from sexual partners”.

Myers sent a link to the FHCRC study referenced in the claims, as well as to an article on Insider that she said correctly summarised the research.

The FHCRC study, “Male Microchimerism in the Human Female Brain”, was published in 2012.

Microchimerism is the existence of small amounts of foreign DNA in the body of an individual.

For the study, FHCRC researchers tested for male DNA in the brain tissue of deceased elderly women. Male Y chromosomes were detected in 63% of the tissue, or 37 out of 59 samples.

The researchers argued that “most likely source of male DNA is from a pregnancy with a male foetus.  In women without sons, male DNA could have been acquired from an abortion or a miscarriage.”

In addition, “male microchimerism could also be acquired by a female from a recognised or vanished male twin, an older male sibling or through a non-irradiated blood transfusion”.

‘No scientific support’

But there is no mention in the study of male DNA being transferred to women during sex. Co-author Dr J Lee Nelson told Insider that “any suggestion that male DNA is routinely retained from sexual partners has no support from any scientific study”.

“To me the biggest statement is the data, if this were routinely happening, I mean, you would see it in the vast majority of adult women (without sons) that we studied,” Nelson said. – Grace Gichuhi


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