Our Selves, Other Cells

Photo: lunar caustic

Is it any solace to sentimental mothers that their babies will always be part of them?

I’m not talking about emotional bonds, which we can only hope will endure. I mean that for any woman that has ever been pregnant, some of her baby’s cells may circulate in her bloodstream for as long as she lives. Those cells often take residence in her lungs, spinal cord, skin, thyroid gland, liver, intestine, cervix, gallbladder, spleen, lymph nodes, and blood vessels. And, yes, the baby’s cells can also live a lifetime in her heart and mind.

Here’s what happens.

During pregnancy, cells sneak across the placenta in both directions. The fetus’s cells enter his mother, and the mother’s cells enter the fetus. A baby’s cells are detectable in his mother’s bloodstream as early as four weeks after conception, and a mother’s cells are detectable in her fetus by week 13. In the first trimester, one out of every fifty thousand cells in her body are from her baby-to-be (this is how some noninvasive prenatal tests check for genetic disorders). In the second and third trimesters, the count is up to one out of every thousand maternal cells. At the end of the pregnancy, up to 6 percent of the DNA in a pregnant woman’s blood plasma comes from the fetus. After birth, the mother’s fetal cell count plummets, but some stick around for the long haul. Those lingerers create their own lineages. Imagine colonies in the motherland.

Moms usually tolerate the invasion. This is why skin, organ, and bone marrow transplants between mother and child have a much higher success rate than between father and child.

Living With Someone Else’s Cells

Of course, we nosy mothers would like to know exactly what our children’s cells are up to while they hang out in us. Are they just biding time in our bodies? Are they mother’s little helpers? Or are they baby rebels, planning an insurgency?

It turns out that when fetal cells are good, they are very, very good. They may protect mothers from some forms of cancer. Fetal cells show up significantly more often in the breast tissue of women who don’t have breast cancer than in women who do (43 versus 14 percent). Why is this? Fetal cells are foreign to the mother because they contain DNA from the baby’s father. One theory is that this “otherness” stimulates the mother’s immune system just enough to help keep malignant cells in check. The more fetal cells there are in a woman’s body, the less active are autoimmune conditions such as rheumatoid arthritis and multiple sclerosis. These conditions improve during pregnancy and for some time afterward — suggesting that the mother’s immune system is more focused on attacking the “other,” not herself. There’s also tantalizing evidence that fetal cells may offer the mother increased resistance to certain diseases, thanks to the presence of the father’s immune system genes. These are new weapons in the war chest.

Some fetal cells have the potential to grow up and be anything. While many of the cells that enter the mother are immune system cells, some are stem cells. Stem cells have magical properties: they can morph into other types of cells (a process called differentiation), like liver, heart, or brain cells, and become part of those organs. Fetal stem cells migrate to injury sites—for instance, they’ve been found in diseased thyroid and liver tissue and have turned themselves into thyroid and liver cells respectively. At the triage sites of wounds they accelerate healing, reducing scars after pregnancy and restoring the normal structure of the skin. It’s striking, the evidence that a fetus’s cells repair and rejuvenate moms. Of course, evolutionarily speaking, the baby has its own interests in mind. It needs a healthy mom.

Then there’s baby on the brain. This is the truly startling stuff. Researchers working with mice have found evidence that cells from the fetus can cross a mother’s brain-blood barrier and generate new neurons. If this happens in humans—and there’s reason to believe it does—then it means, in a very real sense, that our babies integrate themselves into the circuitry of our minds. Could this help explain the remarkable finding that new mothers grow new gray matter in their prefrontal cortex (goals and social control), hypothalamus (hormonal regulation), and other areas of the brain?

Researchers thrill to the possibility of harnessing fetal stem cells to boost the brain, cure cancer and neurodegenerative diseases, and reverse the ravages of age. Fetal cells may be harvested from the blood or organs of mothers and potentially be used as a source of cells with regenerative properties for a mother and her children. They have advantages over other stem cells in that they don’t require the destruction of embryos or require cell cultures and potential contamination. They’re unlikely to be rejected by the mother or child because, from an immune-system perspective, they’re only part “other.”

How we hurt the ones we love

All is well when fetal cells are good, but when they are bad, they are horrid. They have shown up in cancers, and while they may be there to help, there’s also a suspicion that they’re not so innocent. There’s an explanation for this: fetal stem cells may act as cancer stem cells. This isn’t the only potential problem in the relationship. While fetal cells may stimulate the mother’s immune system to be more vigilant, this dynamic can tip into something like violence. A mother’s body may attack the fetal cells within, and in the crossfire her healthy cells get bombarded. The fetal cells themselves may also attack us, the little traitors. What sets off these battles is unknown, but in the fallout, we may suffer autoimmune diseases like scleroderma and lupus.

The maternal cells circulating in a child’s body are no more predictable. Nearly 1 in every 100 cells in a fetus comes from her mom. The population plummets to something like 1 in 100,000 after birth, but enough of a mother’s special agents are still hiding out in her baby’s tissues, and their ranks may be refreshed by refugees in breast milk that slip into the bloodstream.

Maternal cells are busybodies. Some researchers think they train and shape the baby’s immune system and even decrease the risk of allergies. They’re healers too; there’s evidence that maternal stem cells can morph into, for instance, insulin-prod producing cells that proliferate and repair damaged tissue in kids with juvenile diabetes. And, like fetal cells in mothers, maternal cells in children may cause autoimmune problems.

When more than one person’s cells mingle in one individual, the effect is known as microchimerism. The root of microchimerism is the “Chimera,” an animal in Greek mythology. The Chimera is made up of the parts of multiple animals—and so, in a way, are we mothers.

How many people have left their DNA in us? Any baby we’ve ever conceived, even ones we’ve miscarried unknowingly. Sons leave their Y chromosome genes in their mothers. The fetal cells from each pregnancy, flowing in a mother’s bloodstream, can be passed on to her successive kids. If we have an older sibling, that older sibling’s cells may be in us. The baby in a large family may harbor the genes of many brothers and sisters. My mother’s cells are in my body, and so are my daughter’s cells, and half my daughter’s DNA comes from her dad. Some of those cells may be in my brain. This is squirm-worthy.

But there’s something beautiful about this too. Long post postpartum, we mothers continue to carry our children, at least in a sense. Our babies become part of us, just as we are a part of them. The barriers have broken down; the lines are no longer fixed. Moms must be many in one.

Excerpted with permission by Free Press from Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy


    1. This news brought to you from the Department of YMMV. 

      That’s actually one of the reasons I like it. Fetal cells live inside you forever! It’s either gushy and sentimental, or a horror movie plot. You decide!

    1. They need to do way instain mother> who kill thier babbys. becuse these babby cant frigth back? 
      it was on the news this mroing a mother in ar who had kill her three kids. 
      they are taking the three babby back to new york too lady to rest 
      my pary are with the father who lost his chrilden ; i am truley sorry for your lots

    1. Unfortunately, they are the Borg.  Your tactic might work one time but then they adapt and you are again helpless…

    1. Assuming mind and brain are the same, it’s totally possible for cells to live in the brain.

        1. However we have yet to have a mind without a brain. Mind is a subset of brain, not an independent concept.

          Also known as “Why mind transfer devices won’t work without changing the targets brain structures.”

        2. Think, subset.  As in, you can have a brain without having a mind, but you cannot have a mind without having a brain.  Studies of damaged and manipulated brains have shown it exceedingly well.

      1. That is a lot to assume. Materialism is a popular view, not an established scientific fact. You sir are a neural chauvinist!

        1. If the mind is *not* exclusively a product of the brain, then the brain is at least extremely important to the mind. The brain is where much information processing happens, where sensory information goes in, and where motor and metabolic commands go out. This means that the brain is part of the mind, and so a cell in the brain is also in the mind.

        2. Actually, it’s not a lot to assume, and it is an established fact.  Simplest example:  damage an area of the brain and record the behavioral and perceptive changes it produces in the subject’s “mind”.  It can get far, far more subtle than that gross example, too and yet still produce significant results (ie very strong, local magnetic fields affecting memory and mood in test subjects).

          1. My answer to both comments is that systemic dependency is not the same thing as material equality. Which was my subtle point at the top of this post.

  1. Long ago, before the existence of the vaccine, My mom’s B-antibodies and immune cells made mincemeat out of my liver.  I was born neon orange. As the second born, I was extremely lucky to not be dead.  Hurray! (I’m still not dead)

    1. Haha! Same for me. My mom’s body tried to kill me. Now she has an auto-immune disease and her body is killing itself.   Maybe that’ s my fault :/ 

  2. “One theory is that this “otherness” stimulates the mother’s immune system just enough to help keep malignant cells in check. The more fetal cells there are in a woman’s body, the less active are autoimmune conditions such as rheumatoid arthritis and multiple sclerosis.”

    No, actually.  Women are significantly more likely than men to develop auto-immune disorders, and research is suggesting that fetal cells are a likely part of the explanation.

    1. If you read on, Jena mentions this as well. It sounds like there’s some mixed effect going on here. Fetal cells can cause auto-immune disorders, but they might also be protective in some cases, depending on factors we don’t understand very well yet. 

      1. But don’t let that stop the positive spin on the gushy love fest of how great pregnancy is supposed to be for women. Because it’s not like there’s ever been an agenda surrounding that or anything. Like, ever. And it’s not like rampant slanting and emotionally loaded reads of scientific experiments have ever been used as propaganda. It sounds to me like it’s pretty biologically neutral, with consequences and benefits that really don’t merit saying much except “yep, something happens” right now.  Forgive my cynicism, if you can.

        1. I’ve only met one woman that had that pregnancy experience that matched how “great” it was supposed to be.  And truth be told, she’d somehow find bliss in being water tabled; she goes through the world with that facial expression people used to get while watching the Lawrence Welk Show.  You know, the glazed eyes & social “See, I’m happy” smile…  Can I join you in that cynicism?

          Pregnancy is a method mammals use to survive as a species and ensure genetic variation.  There’s lots of physical stress and discomfort and it’s dangerous, and there’s some emotional manipulation going on, like when bliss hormones and love hormones and all that are released.  But those are nature’s way of ensuring primates will have more than one single-child litter. 

          As social creatures we can help each other during difficult times, forming optimistic traditions and supportive memes.  But the (okay, I’ll say it:  somewhat paternalistic) meme of modern women preferring to be home, in the kitchen and pregnant as part of some Glorious role fulfillment or advertiser’s dream world diva has got to go.

          1. i’ve never met anyone who had a baby who thought it was bliss.  i can’t say i’ve experienced any particular agenda in that regard — if anything, women LOVE to tell pregnancy war stories!  seriously, get a room of mothers going, it’s like bragging rights.  mine was uneventful and pleasant until the very end when all hell broke loose, here, sit down and i’ll tell you all about it ….

          2. I’ve had a couple of friends who loved being pregnant, but they weren’t the majority.

          3. I’ve had a fantastic pregnancy, enjoyed it a lot more than I expected (partly because I had heard many more horror stories- and ubiquitous, dumb stereotypes- about it than happy ones)… and I’m about as far from being a Stepford wife as one can get (though I readily admit that labour was a total @#$%& bitch to me).

            I wish it were possible for women to either hate OR love something, or want OR not want something without getting singled out and judged either way.

    2. I agree… but… I have lupus and have never been pregnant- no, not even with a fetus that miscarried without me knowing it- I’m a lesbian. I would believe that in this case it is the cells working the other way- my mother’s cells, some of which may have been her mother’s cells, or those of her older sister, both of whom have/had lupus. This is all so fascinating. 

      1. Absolutely.  Auto-immune disorders run on one side of my family.  We’ve all had kids, and pregnancy definitely exacerbated our medical situations, but the family genes were already there, ready to be turned on.  Some of the new research on MS (one of the diseases that runs in the family) suggests that it’s a common virus that sets the genes off.  Pregnancy is a huge stressor, but there are plenty of others….genes are the real cornerstone.

  3. “One theory is that this “otherness” stimulates the mother’s immune system just enough to help keep malignant cells in check. The more fetal cells there are in a woman’s body, the less active are autoimmune conditions such as rheumatoid arthritis and multiple sclerosis. These conditions improve during pregnancy and for some time afterward — suggesting that the mother’s immune system is more focused on attacking the “other,” not herself.”

    I wasn’t taught this in my cancer biology and immunology classes in grad school; rather, it was that pregnancy acts as a mild immunosuppressive to dial down the mother’s immune responses and protect the “foreign” fetus (one supporting piece of research at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1782465/ and many more available with searching). It would also explain the improvement in the autoimmune diseases. This is why women who have previously had melanomas have higher rates of recurrence or metastasis during or immediately after pregnancy – because her immune system had previously held the cancer cells in check, but the immunosuppressive state of her pregnancy allowed the cells to proliferate and spread. Unfortunately it’s a lot less warm and fuzzy of a theory.

    1. And women who have never had children have a higher risk of breast cancer.  Women can’t win for losing or so it seems.

        1. So, are you saying a woman who has her first birth when she’s 30  has the same risk of a woman who has never given birth? I mean, the story line for the past 30 years has been a woman is more likely to develop breast cancer if she has never had children. I think they even cited statistics from women in convents. Well, cold comfort all around, I’d say.

          1. Researchers looking at centuries of records in Britain determined that the fewer the children (including none), the longer the woman will live. And the older the woman when she has her first child, the longer she’ll live. Despite the breast cancer risk, having children still shortens your lifespan.

        2. P.S. Diane,  Nulliparous? Get real. Get human. Again, cold comfort. Yikes! Exactly what I mean. Get pregnant before 30 or suffer the consequences. I don’t buy it. What you are saying is for a woman’s best chance of a healthy life she has to have children. Why do these rules never apply to men?

          1. I am not saying anything. I am simply sharing the NCI’s claims. They also say that ” Breast cancer risk is transiently increased after a term pregnancy. (1).” I am not a scientist, I don’t know how much of that is true. As a 30 year old woman who chose to not have children,  I am definitely not saying that in order to have a healthy life  women should have children.  I’ve known women who had children early and still had breast cancer, so I think it’s more complicated than that. But again, this is just my experience. If I ended up having cancer because I did not procreate, I will deal with it, but I will never tell what women should do with their bodies.  (Forgive my grammar, English is my second language).

    2. I was about to reply with this fact as well! It is NOT that the mother’s body is attacking the “other” better and ignoring the mother, it is that the mother’s body has lowered her ability to attack anything (sperm, fetus, the mother, common infections, etc). I have multiple sclerosis which I was diagnosed with years before my pregnancy (and which I most likely suffered from for the decade prior to diagnosis). Pregnancy was one of the best times of my life as my MS was in full remission. It remained so until about 4 months after pregnancy where my body flared up with one of the worst exacerbations I’ve ever had. Right now they are researching how to administer this immunosuppressive in a pill form to help decrease the effect of autoimmune diseases on the body.

  4. I also find it fascinating how quick and varied our flora takes up residence in our guts, on our skin, etc. I always wondered if some bacteria was already in the gut from the mother at birth.

  5. Any evidence that fetal stem cells can migrate to the ovaries and become ova? Seems like if this were possible, natural selection would favor it…

    1. Strictly speaking, ova derived from fetal cells would share only half the mother’s genes, which is effectively a 50% genetic penalty for the mother compared to children produced from her own ova. So this would favor the father’s genes, not the mothers’ genes, and it would be in the mothers’ genes’ best interest to prevent this.

    2. The ova are already formed, if not yet matured at puberty and before.  So I’d say that unless the fetal stem cells can act as viruses and inject their DNA or swap like bacteria, the chances are pretty much zero.

  6. Think about twins. Twins of opposite gender  share male and female hormones in vitreo. Maybe that’s the best of all possible worlds where a man and a women somehow have an understanding insight into the psyche of the other and are able to use that throughout their lives. I know whereof I speak.

  7. call me crazy, but i don’t find this particularly “squirm-worthy.”  i built it inside me, and little bits of it stayed, like sawdust.  sounds reasonable.  man, people are so squeamish in this day and age.

    1. Yes, but what if it was non-consensual and an egg fertilized and implanted?

      …his cells in you forever, in your brain, your heart…just when you thought the violation couldn’t possibly be greater, new information comes along.

      THIS is why Plan B is needed, over the counter &  to anyone who wants it.

      1. of course it should be, but that’s a separate issue.  anyway, once the egg is fertilized and implanted, even if you dislodge it, this is claiming that a bit of cell stays behind, though i imagine it matters how long it was there.  it doesn’t strike me as an instantaneous thing.

        if this is how the body works, that’s how it works, whether it grosses you out or not.  let’s not get mystical or torture ourselves with deeper meaning.  it seems weird to me to get upset over what your body does and has always done since the beginning of time.  it’s like people who are horrified by menstruation or something, i don’t get it. 

        1. That’s a really good point, Dahlia.   I’m going to guess not many cells go back and forth until the placenta is developed and there’s a circulatory system to work with.

          It *is* the way the body works and there is *nothing* mystical about it other than what people choose to believe (in other words, there is an objective reality under it all).   Nor is it “gross”.  But I have trouble seeing it as “spiritual”, too.  It’s more…mechanical, I guess.  Spiritual is what’s in your head (as is deciding what’s gross and what’s beautiful).

          The only deeper meaning I was gleaning was in the special case of rape.  It struck me that what was explained in this report could make it emotionally far worse and really does point out the need for the choice I mentioned.

  8. I don’t understand how a cell can pass through the hematoencephalic barrier, is that possible now??

    1. Some T-cells can and do on a regular basis, seemingly as part of regular um, maintenance.  And, the BBB is much more permeable during inflammation.  *and* sometimes when some of those T-cells get inside, they incorrectly initiate an inflammation response and let other stuff in. 

  9. Augh, you’re being requoted (kottke) on details you got wrong.

    “In the first trimester, one out of every fifty thousand cells in her body are from her baby-to-be (this is how some noninvasive prenatal tests check for genetic disorders). In the second and third trimesters, the count is up to one out of every thousand maternal cells.”

    Your numbers are for the fraction of fetal cells in the BLOOD, which constitute a very small fraction of the total number of cells in the mother’s BODY.

  10. Don’t forget about all the DNA you’re harboring from the cows and pigs and chickens and tomatoes and stuff that you eat. Mmmm yummy DNA soup! http://www.newscientist.com/article/mg15320637.800-science–can-dna-in-food-find-its-way-into-cells.html

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