Most people can easily think of that one ex-lover they wish they could erase from their past, and would love to pretend it never happened. Unfortunately, recent articles and research hints that it may be possible for DNA from an ex-lover to continue to live on inside women. Let’s explore this claim in more detail.
Do Women Retain DNA from Every Man They Have Ever Slept With?
Just the thought of this sounds bizarre and more than likely undesirable, but that’s been the claim circulating the internet for a while now; namely that women absorb and retain DNA from every man they have had intercourse with.
The study that spurred on this idea was published in the journal PLOS One in 2012, entitled “Male Microchimerism in the Human Female Brain.” Microchimerism is:
“In humans (and perhaps in all placentals), the most common form is fetomaternal microchimerism (also known as fetal cell microchimerism or fetal chimerism) whereby cells from a fetus pass through the placenta and establish cell lineages within the mother.”
During the study, researchers discovered that “63% of the females (37 of 59) tested harbored male microchimerism in the brain. Male microchimerism was present in multiple brain regions.” In other words, genetic material from a male was found in the brains oof the women who participated in the study.
What was most fascinating about their research was that only male cells had passed through the blood-brain barrier. That ‘barrier’ is a semi-permeable membrane that would have otherwise blocked most chemicals in your bloodstream from entering the brain.
So, Do Women’s Bodies Keep Genetic Material From All Their Partners?
However, contrary to other articles covering this study, researchers do not actually mention intercourse.
In fact, they hypothesize that “the most likely source of male microchimerism (Mc) in female brain is acquisition of fetal Mc from pregnancy with a male fetus. In women without sons, male DNA can also be acquired from abortion or a miscarriage.
The pregnancy history was unknown for all but a few subjects in the current studies, thus male Mc in female brain could not be evaluated according to specific prior pregnancy history. In addition to prior pregnancies, male Mc could be acquired by a female from a recognized or vanished male twin, an older male sibling, or through non-irradiated blood transfusion.” 
Basically, they couldn’t know exactly where this DNA came from, but they don’t think it’s from sexual partners.
But, Some People Think the Researchers’ Explanation Is Insufficient
According to YourNewsWire however, two studies actually do seem to point towards the possibility of male DNA coming from sexual partners. The first study is from 2005 and was published in the American Journal of Medicine. It actually does reveal that, in some cases, women who had never given birth to males (or at all) had male cells inside of them.
Another 2015 study published a decade later in the journal Chimerism examined 154 girls, 21 of whom tested positive for male microchimerism. However, the data suggested that the male DNA likely originated “from an older brother either full born or from a discontinued pregnancy or from transfusion during pregnancy.”
So, although more research is definitely needed to make any definitive claims about this fascinating topic, the reality is definitely interesting, but for reasons other than we may think.
 Chan, W. F., Gurnot, C., Montine, T. J., Sonnen, J. A., Guthrie, K. A., & Nelson, J. L. (n.d.). Male Microchimerism in the Human Female Brain. Retrieved December 13, 2017, from http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0045592
 Dmitry, B. (2017, June 25). Women Absorb And Retain DNA From Every Man They Have Sex With. Retrieved December 13, 2017, from http://yournewswire.com/women-dna-man-sex/
 Yan, Z., Lambert, N. C., Guthrie, K. A., Porter, A. J., Loubiere, L. S., Madeleine, M. M., . . . Nelson, J. L. (2005, August). Male microchimerism in women without sons: quantitative assessment and correlation with pregnancy history. Retrieved December 13, 2017, from https://www.ncbi.nlm.nih.gov/pubmed/16084184
 Müller, A. C., Jakobsen, M. A., Barington, T., Vaag, A. A., Grunnet, L. G., Olsen, S. F., & Kamper-Jørgensen, M. (2015, October 02). Microchimerism of male origin in a cohort of Danish girls. Retrieved December 13, 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27623703
 FACT CHECK: Do Women Retain DNA From Every Man They Have Ever Slept With? (2017, August 22). Retrieved December 13, 2017, from https://www.snopes.com/women-retain-dna/