“I carry your heart with me. (I carry it in my heart)”. This line from an E.E. Cummings poem has always resonated with me, but recent medical research provides a powerful new meaning for these words.
This poem has been interpreted as referring to the romantic love the speaker carries for his beloved, but the same can be said of a mother’s love. The maternal bond can be a powerful connection between mother and child and has the ability to transcend physical space and time. This is no exception for the loss of a child whether through miscarriage, stillbirth, or any point during the child’s life, including adulthood. In fact, a common theme when doing grief work is to hear a mother refer to her deceased child as remaining “always in my heart”. Remarkably, recent research supports that through a process known as fetal microchimerism, this might quite literally be true.
Starting in early pregnancy, fetal cells and DNA cross the placenta and can be detected in the maternal blood as soon as the first trimester. Some cells migrate to maternal organs including the lung, skin, thyroid, kidney, liver, and heart. The number of fetal cells and DNA present in a mother’s blood plasma and serum clears drastically by two months postpartum, but some cells may remain in the maternal blood and tissue for decades. Researchers at Tufts Medical Center found male XY chromosomes and fetal cells in a mother’s blood twenty-seven years after she had given birth.
In a reciprocal process, maternal cells and DNA also have been found to transfer to the fetal blood, pancreas, skin, and heart. One study found that over half of the adults studied still had maternal cells in their blood (including maternal cells from grandmothers). Additionally, since fetal cells can remain in the blood and tissue for years, the fetal cells of one sibling can also be passed to those of their younger siblings. Is it any wonder then that immediate family is referred to as “blood relatives”?
Scientists are not certain of the exact purpose for sharing fetal cells in pregnancy; however, it is believed that these cells may contribute to a mother’s healing process. Current research is looking at how fetal microchimeric cells may function as reparative stem cells in pregnant individuals who are having medical complications. For example, fetal cells have been found to have morphed into the damaged liver and thyroid tissue to assist in restoring function in these maternal organs. Fetal cells have also been found to have differentiated and participated in tissue repair in mothers who had appendectomies during pregnancy. Another study found fetal cells present in the healed maternal scars resulting from c-section births and are believed to play a key role in the collagen production that is needed for postpartum healing.
Scientists are studying whether microchimeric fetal cells and DNA might be directly responding to signals sent from injured maternal tissue and then differentiate into specialized stem cells. Specifically, in a study by Kara et al., researchers evaluated how fetal stem cells proliferated and showed “selective and specific homing” to the heart in women who were having serious cardiac complications during pregnancy. It is thought that these fetal cells may play a critical role in repairing the damage done to the maternal heart muscle. Medical researchers are focusing on the vast potential applications for treatment, prenatal diagnosis, and other medical advancements that can be gained from further studying fetal microchimerism. However, from the perspective of a grief therapist, and grieving mother, the psychological implications of these studies might be even more astounding. How comforting for a grieving mother to know that cells from her own child remain with her for decades and may help to mend a broken heart.
Julianne Massimo, May 2023
References
Bianchi, D. W., Zickwolf, G. K., Weil, G. J., Sylvester, S., & DeMaria, M. A. (1996). Male fetal progenitor cells persist in maternal blood for as long as 27 years postpartum. Proceedings of the National Academy of Sciences, 93(2), 705-708.
Boddy, A. M., Fortunato, A., Wilson Sayres, M., & Aktipis, A. (2015). Fetal microchimerism and maternal health: a review and evolutionary analysis of cooperation and conflict beyond the womb. BioEssays, 37(10), 1106-1118.
Comitre-Mariano, B., Martinez-Garcia, M., García-Gálvez, B., Paternina, M., Desco, M., Carmona, S., & Gómez-Gaviro, M. V. (2022). Feto-maternal microchimerism: Memories from pregnancy. Iscience.
Gammill, H. S., & Harrington, W. E. (2017). Microchimerism: defining and redefining the prepregnancy context–a review. Placenta, 60, 130-133.
Kara, R. J., Bolli, P., Karakikes, I., Matsunaga, I., Tripodi, J., Tanweer, O., ... & Chaudhry, H. W. (2012). Fetal cells traffic to injured maternal myocardium and undergo cardiac differentiation. Circulation Research, 110(1), 82-93.
Mahmood, U., & O’Donoghue, K. (2014). Microchimeric fetal cells play a role in maternal wound healing after pregnancy. Chimerism, 5(2), 40-52.
Orlova, K. (2020, May 10). Mother’s Day Genetics: How long does a mother “carry” a child? Ariel Medicine. https://arielmedicine.com/mothers-day-genetics-how-long-does-a-mother-carry-a-child/
Zimmer, C. (2015). A Pregnancy Souvenir: Cells that are not your own. New York Times. https://www.nytimes.com/2015/09/15/science/a-pregnancy-souvenir-cells-that-are-not-your-own.html
