FactCheck Social Media

Male DNA ‘living forever’ in women after sex is short on evidence

2021-06-04 15:39:08

The Statement

A social media post claims that if a woman has sex with a man, his DNA lives in her forever.

The Facebook post from May 19 features an image of a man and women wrapped in chains and engaged in a sexual act. The post is headed: “Recent research on DNA transmission via sex.”

The text of the post goes on to say, “If you have sex with a man, his DNA lives in you forever. A research (sic) by university of Seattle USA has proven that. There is now a greater understanding of why God asks us not to have sex before we get married. This research proves that any man, that a woman has sex with leaves a part of his DNA in the woman. The man who has had more sex with her, leaves more of his DNA in the woman. So when a woman ovulates, the eggs that she produces contain more of other DNAs.”

The post goes to say the study found the presence of genetically distinct male cells in the brains of women, called “microchimerism”.

“This also means these other male cells will be found in a fetus when the woman gets pregnant,” it says.

The post by a page in Papua New Guinea had been viewed more than 16,000 times and shared more than 175 times at the time of writing.

The Facebook post from May 19
 A Facebook post claims that if a woman has sex with a man, his DNA lives in her forever. 

The Analysis

The study that appears to be the source of the Facebook post’s claims does not suggest that a man’s DNA is transferred into a woman during sexual intercourse.

The idea that women carry the DNA of their sexual partners can be traced to a 2017 article from YourNewsWire, a frequent source of misinformation. The article cites a “new” study from researchers which purportedly showed “women retain and carry living DNA from every man with whom they have had sexual intercourse”.

However, the study it referred to – published in the medical journal PLOS One in 2012 – was not new at the time of either the 2017 article or the Facebook post’s publication. The study, titled “male microchimerism in the human female brain”, was also misidentified in both cases as involving researchers from the University of Seattle.

Instead, it involved academics from Seattle’s Fred Hutchinson Cancer Research Center and the University of Washington in Seattle. One of the Fred Hutchinson centre’s labs focuses on the concept of “microchimerism”, which it says most commonly involves the exchange of DNA between mother and child during pregnancy.

Identifying the existence of male cells in the bodies of females is not new, as this blog post published by PLOS about the research pointed out. For example, it cited 1996 research that found pregnancy set up a “long-term, low-grade chimeric state in the human female”.

The significance of the 2012 study was to demonstrate for the first time the presence of genetically distinct male cells in the brains of women, whose bodies were examined during autopsy. However, it does not mention sexual intercourse as a source of the foreign DNA.

Rather, it states: “The most likely source of male (microchimerism) in female brain is acquisition of fetal (microchimerism) from pregnancy with a male fetus. In women without sons, male DNA can also be acquired from an abortion or a miscarriage.”

The study noted the pregnancy history was not known for all of the subjects, which meant pregnancy as a source of the DNA could not be properly evaluated. Other possible sources of the male DNA were stated as: “A recognised or vanished male twin … an older male sibling, or through non-irradiated blood transfusion.”

Nevertheless, other studies have speculated that sexual intercourse could be one of several potential sources of male cells found in women and girls. A 2016 Danish study and a 2005 study from Fred Hutchinson Cancer Research Center academics both raised intercourse as a possible source of male microchimerism, but neither investigated the supposition in depth.

None of the studies support the post’s claim that all men leave part of their DNA in a woman during sex, nor that this purported foreign material is then transferred into the woman’s eggs and children.

One of the 2012 study’s authors, Professor J. Lee Nelson, who leads a research team at the Fred Hutchinson centre, told Insider in 2018 there was no scientific evidence to suggest male DNA was routinely retained from women’s sexual partners.

She added that data did not support the speculation, noting that “if this were routinely happening … you would see (male microchimerism) in the vast majority of women that we studied”.

Mike Garratt from the Department of Anatomy at Otago University, whose area of research includes the consequences of mating for health and ageing, told AAP FactCheck there was evidence in mice that male seminal fluid caused an immune response in females – but that wasn’t the same as male DNA staying in the female body for a lengthy period of time.

“I don’t think that there is evidence that male DNA gets into the female brain as a consequence of seminal fluid exposure,” Dr Garratt said in an email.

Professor Sarah Robertson from the Faculty of Health and Medical Sciences at the University of Adelaide agreed there was some evidence from mice and other mammalian species that sperm-derived DNA could persist in the female reproductive tract after sex. But whether that built up over time with repeated matings was unknown.

As to whether a similar transmission could occur in humans, Prof Robertson said it had not been investigated, to her knowledge.

A young couple lies in bed.
Research hasn’t shown a link between sex and the presence of male DNA in some women. 

The Verdict

The claim in the Facebook post that male DNA remains in a woman after sex and that DNA builds up with every act of sexual intercourse is not supported by the study it appears to refer to. This research did not list intercourse as a source of male microchimerism in women.

Other studies have suggested sexual intercourse as one of several possible causes of microchimerism, however the link is currently only speculative. There is no suggestion in any of the research that this potential DNA transfer could apply to every sexual act between a man and a woman, as stated in the post.

False – Content that has no basis in fact.

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