There are so many things in motherhood that come as a surprise. And there are so many new things to worry about. But scientists have discovered even more reasons to be in awe of the female body after conception. Have you ever heard of fetal microchimerism? Chimera, a mythical Greek creature with three different heads, wings and a snake for a tail, is an explanatory example of motherhood today – being several things at once. But motherhood can also mean another thing — being yourself, and within you, literally someone else. The belief that a child is always a part of you is quite literally at the cellular level in a mother’s body tissue. During pregnancy, nutrients from the mother cross through the placenta and into the baby, and fetal cells cross back into the mother and assimilate This is referred to as fetal microchimerism.
Does that leave mothers at a higher health risk? Or do the fetal cells actually help immunize our bodies against cancer and other issues? How can fetal cells benefit mothers? All this and more will be answered in this post.
What is a Fetal Microchimerism?
Fetal microchimerism is when cells from the fetus pass through the placenta and become part of the mother’s body. They can persist for decades in the body, acting like the cells in the tissues surrounding them. The fetal cells can act like stem cells. After becoming lodged in tissues, they can use chemical cues from neighboring cells to assimilate.
There have been different kinds discovered, including placenta cells, stem cell-like fetal cells, and cells with different antibodies. Cells with Y chromosomes have also been found in the bodies of women.
Fetal microchimerism is just one variation of microchimerism. Cells can also be absorbed from a vanishing twin, shared cells from a twin in the womb, or being a mosaic person, having two sets of genomes being created from a single cell. Chimerism has also been seen in individuals with a highly compromised immune system who received a blood transfusion after a trauma.
Fetal microchimerism may not just occur in humans — it happens in all mammals that carry placentas during pregnancy.
How Does Fetal Microchimerism Affect Us?
Chimerism was discovered decades ago when male DNA was found in a woman’s bloodstream. However, technology is just now becoming advanced enough to study this cellular phenomenon.
In studying microchimerism, research often tracks male DNA, which is easier to spot in a mother’s body. The organs found to have male fetal cells were found more frequently in the lungs, spleens, livers, kidneys and hearts of pregnant mothers. This may be attributed to the path of blood flow in the mother’s body. In this scenario, cells are trapped as they travel around the body through the bloodstream.
The number of cells in a mother’s body may depend on the number of pregnancies she’s had, or her immune system. The immune system can attack traveling fetal cells. Consequently, the number of fetal cells present vary depending on the ‘killer cells’ the mother has in her body. They also vary according to how quickly they join tissues.
This research supports the role of fetal microchimerism in autoimmune disease, pregnancy complications, and certain cancers, though it has not been proven. However, we are starting to see possible links between fetal cells and their benefits and detriments to both mothers and their families.
Fetal Microchimerism Can Benefit Immunity-Deficient Offspring
In cases of high-risk leukemia and other immune diseases where there were no human leukocyte antigen matches, patients fared better when they received a transplant from their mother than from their father. The study concluded that a mother with a higher number of fetal cells present may make better donors for children with those conditions.
Fetal Microchimerism May Protect from Neurological Diseases
One study that researched the amount of male DNA in women’s brains suggested that there may be a link between male DNA cells and conditions like Alzheimer’s. The women with male DNA found in the brain had lower rates of neurological disease. The samples came from a variety of ages, including one 94-year-old woman, but not all pregnancy histories were known. Therefore, without sourcing the male DNA as being exclusive from carrying a male pregnancy (microchimera also existing after vanishing twins or miscarriages), a definite conclusion could not be made.
Fetal Cells Could Help Repair Injured Tissue
A 2011 study showed fetal cells traveling to affected heart tissue in mice and changing into different heart tissue cells. Presumably, they chose the injured tissue over healthy tissues. Fetal cells may work to ensure a mother’s health. This reasoning may be related to the higher survival rate of heart disease in pregnant mothers. 50 percent of pregnant women recover spontaneously.
Fetal Microchimerism Could Affect Future Pregnancies
There is the idea that previous pregnancies can affect the ability to get pregnant again. Cells from a previous fetus could assimilate into the mother and then be shared again into a younger sibling. Therefore, creating a more complex chimera and possibly affecting that and future pregnancies. Scientists are noting that fetal microchimerism is promising for explaining unexpected pregnancy loss or issues getting pregnant again.
Fetal Cells Affect Cancer, But How?
There is not definite proof that fetal cells affect cancer in one way or another, since they have shown to both suppress and contribute to the disease. In studies, they have shown to act like cancer stem cells as they infiltrate and copy the surrounding tissue. They have also been found in higher rates in diseased organs than in non-diseased bone marrow of the same patient.
With breast cancer, the possibilities are even more confusing. One study showed lower chances of breast cancer among women who had more than one pregnancy. While other studies show higher chances with women who had an oversupply of milk production and higher-grade tumors with the presence of fetal cells.
What’s Next In Research
Researchers are looking to deep-sequencing technology to differentiate fetal cells from the cells of the mother. This will allow them to further study their impact.
The relationship between fetal cells and surrounding tissues seem to vary depending on the location. They also vary according to the health and genetics of the mother. The writers of a large 2015 study reviewing previous research of fetal cells are using evolutionary reasoning to guide the next steps of research. They predict that fetal cells have a role in tissues that have a role in transferring resources to the fetus. Those include the brain, which has a role in maternal attachment and neural circuitry. They also include the breast, where fetal cells may affect milk production. Finally, they may include the thyroid, which affects heat transfer and metabolism.
“If these fetal cells are interacting with maternal physiology, where in the maternal body would we expect the greatest effect on function? That’s been a big question mark,” said Julienne Rutherford, a biological anthropologist at the University of Illinois at Chicago. She told Smithsonian, “Putting this into an evolutionary context was incredibly clever and novel and very exciting. It’s a beautiful example of theory driving testable predictions.”
Could This Explain Your Lifelong Connection To Your Child?
Now that science has established we are literally part of our children and they are part of us, could this explain some other things that happen to moms that are not explainable? Like how mothers know when their children are in trouble? OR when some mothers know their child is still alive after they have gone missing for years and others give up? What else do you think they will discover?