As a mother of three, there is no doubt in my mind that there is a physiological bond between mothers and their children that extends beyond pregnancy and even after birth. But this is more than my personal experience and opinion. Biologically, women and their children are connected at a cellular level for десятилетия after a pregnancy has ended, through a process called maternal-fetal microchimerism.
What is maternal-fetal microchimerism?
Maternal-fetal microchimerism is the process by which maternal cells transfer to her fetus and fetal cells transfer to the mother [1]. These cells could remain in place for the rest of each of their lives!
This process likely begins around six weeks of pregnancy, and continues until the end of the pregnancy. If the mother decides to breastfeed after birth, microchimerism continues with maternal cells transferring to the baby through her breastmilk [2]. Perhaps even more fascinating, maternal-fetal microchimerism has been found to occur not only between a mother and her unborn child, but also through cells transferring to the fetus left behind by his or her older siblings—and even from his or her maternal grandmother [1].
Maternal-fetal microchimerism has been found to occur not only between a mother and her unborn child, but also through cells transferring to the fetus left behind by his or her older siblings—and even from his or her maternal grandmother.
Maternal-fetal microchimerism is primarily seen in animals with placentas [1]. It is believed that the placenta helps to enhance how nutrients are transferred from the mother to the baby, as well as to increase the amount of cells transferred between the two.
What does the research say about maternal-fetal microchimerism?
There is still much to be learned about maternal-fetal microchimerism, but there is more research being done to determine the purpose of this process and its benefits and risks.
Benefits of maternal-fetal microchimerism
Согласно 2024 review from researchers based in the Czech Republic, the cells transferred to the fetus’s body via the umbilical cord and the placenta have primarily been identified as immune cells, indicating that one purpose and benefit of maternal-fetal microchimerism is the strengthening and establishment of the child’s immune system [3]. Again, if the mother chooses to breastfeed, this immune system benefit continues after birth as the mother’s cells are transferred to her baby through her breast milk.
For the mother, the process of maternal-fetal microchimerism also has some positive effects. In a 2015 review of the literature from Bioessays, the authors aimed at providing an evolutionary framework to evaluate the microchimerism process. As the review tells us, the cells transferred from the baby into the mother’s body often act like stem cells to improve the function of a variety of her body systems: “It is in the fitness interest of the offspring to enhance maternal survival and contribute to maintenance of the maternal body. This predicts that fetal cells may take over stem cell niches, which may be associated with greater survival and reduced aging of mothers” [1].
The cells transferred from the baby into the mother’s body often act like stem cells to improve the function of a variety of her body systems.
What’s more, these fetal cells will go on to specialize within the particular section of the body in which they “land,” i.e., if a stem cell settles in the brain, it becomes a brain cell. These fetal “stem cells” have also shown to enhance wound healing for the mother and lessen the effects of aging. For example, they have also been found clustering at places of inflammation and playing a role in healing C-section scars.
It may be consoling for those who’ve experienced miscarriages or abortions to learn that fetal cells remain after every pregnancy, even very early miscarriages or abortions. Mothers mourning the loss of their pregnancies can find some solace in the biological fact that they are forever connected to their children.
It may be consoling for those who’ve experienced miscarriages or abortions to learn that fetal cells remain after every pregnancy, even very early miscarriages or abortions. Mothers mourning the loss of their pregnancies can find some solace in the biological fact that they are forever connected to their children.
Risks of maternal-fetal microchimerism
As incredible as maternal-fetal microchimerism is, there can also be risks to this mother-child intercellular interaction. As the 2-15 review from Bioessays points out, because parents and their children do not share all of the same genetic material, there is bound to be some conflict when cells are exchanged. In fact, maternal-fetal microchimerism could be one part of the cause behind some prenatal conditions like гестационный диабет и преэклампсия.
Outside of prenatal conditions, women are at a higher risk for developing thyroid conditions and autoimmune diseases postpartum, which some researchers have suggested could be related to the introduction of fetal cells to the mother’s body. It has also been noted that cell transfer seems to prioritize the health of the child over that of the mother, often leading to a depletion of resources for the mother.
What still needs to be understood?
Scientists still do not completely understand the purpose of maternal-fetal microchimerism or all of its benefits and risks. More research needs to be done to fully explain how maternal-fetal microchimerism affects the development and strength of the child’s immune system, and how maternal-fetal microchimerism contributes to a mother’s health positively and negatively during pregnancy, postpartum, and beyond.
Как Bioessays authors note, more research into maternal-fetal microchimerism may yield “potentially important implications for our understanding of health and disease pathology, including lactation science, thyroid diseases, autoimmune diseases, cancer and even maternal emotional, and psychological health postpartum.” Furthermore, as the Czech researchers note, “future discoveries of additional phenomena related to maternal microchi-merism will not only be relevant to immunology but also to other fields such as tissue regeneration, cancer biology, various biological therapies, and organ transplantation.”
More research into maternal-fetal microchimerism may yield “potentially important implications for our understanding of health and disease pathology, including lactation science, thyroid diseases, autoimmune diseases, cancer and even maternal emotional, and psychological health postpartum.”
For now, however, maternal-fetal microchimerism remains possibly one of the most fascinating and least understood processes that occurs during pregnancy. But for many mothers and their children (even those lost in miscarriage and abortion)–the science of maternal-fetal microchimerism confirms a knowledge that’s (literally!) “bone deep:” we are forever connected to our children (and even our grandchildren) at an intercellular level.
