When people say that pregnancy changes your body forever, they’re usually talking about stretch marks. But here’s a way that pregnancy can alter a woman that goes far below the surface, deep into the tissues and neurons of the her body. It’s one of the coolest bi-products of pregnancy and it has powerful implications for our health.
Emerging research shows that fetal cells can linger in mom’s body long after pregnancy, sometimes repairing injuries and instigating cell and tissue growth.
Here’s how it works: Fetal cells somehow cross into mom’s body during pregnancy, probably via the placenta. The presence of these cells in mom’s blood stream is strongest in the last trimester and then plummets after birth, but some cells stick around and start their own lineages. (A new study, published today, has identified several kinds of fetal cells in mother mice.)
These cells can be found in various organs in the mother years after the baby is born and often they’re associated with repairs to the mothership.
According to Jena Pincott, who writes eloquently on the subject in her book, “Do Chocolate Lovers Have Sweeter Babies,” they seem to protect women from some kinds of cancer. There are more fetal cells in the breasts of women who do not have breast cancer than those who do (43% v. 14%). They can also be found at injury sites, accelerating healing and reducing scars. They have been found in diseased liver and thyroid tissue.
An NPR report on this phenomenon included an incredible story about a woman with signs of hepatitis. Doctors found damaged liver tissue, but along with it, tons of fetal cells. “We found hundreds and hundreds,” said Dr. Kirby Johnson of Tufts University. Typically, they’d find maybe a dozen, but in this case there were “literally sheets of cells — whole areas” in the liver, and they seemed to be turning themselves into healthy cells. This women had, over her lifetime, five conceptions (one child, two miscarriages and two abortions). The woman declined treatment but months later at a check-up the doctors found that she was completely healthy. Her liver had somehow repaired itself. One hypothesis is that the fetal cells from her pregnancies were involved.
Pincott writes, “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.”
It’s unclear how these cells work; they may boost mom’s immune system or the DNA from dad’s immune system may be an extra perk to mom or the fetal cells may turn into other cells to repair tissue damage. Or all of the above.
In studies involving mice, it appears that fetal cells cross the blood brain barrier and actually generate new neurons in the mother mouse’s brain. (You may feel like a dunce at the end of pregnancy but we know that there’s increased brain growth in mothers in the months following. Perhaps these fetal cells have some hand in that? )
But Pincott points out that while these cells can be very, very good, “when they are bad, they are horrid.” The cells have shown up in some cancers and while they might be helping they could, in some instances, be contributing to cancer growth. Also stimulation of the mom’s immune system may get a little too vigilant which could, theoretically, lead to an auto-immune disease like scleroderma or lupus. My guess is that fetal cells are neither totally good nor totally bad.
When I was in college studying feminist theory, I came across a phrase I’ll never forget– I believe it was from the French feminist Luce Irigaray. She wrote, “woman is always one and becoming.” The story of these fetal cells reminded me of that beautiful line. We are one but we are also, sometimes, more than one. As Pincott observes, “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.”