Definition of Fetal-maternal Microchimerism
Glossary
Definition: Fetal-maternal Microchimerism
by Stephen Michael Leininger
Posted: 06/24/2022
Updated 08/15/2026
STOSS Books
Science is now showing us the degree to which the phrase, one-flesh union, describes both theological and biological scientific truths. The term one-flesh is not merely a metaphor, but is literal. The following is not the only example of the literal meaning of the term, one-flesh. It is one of many examples. Science has now revealed that the one-flesh relationship between Jesus and Mary goes far beyond our historical understanding. While researching this article, I came across a biological phenomenon known as fetal-maternal microchimerism.
Researchers at Arizona State University[1] have shown that mothers retain some of their babies functioning cells, even up to the time of their own death in their 70’s.[2] These cells can reside in any organ in the body. As with all fetal stem cells, they can differentiate and become beating heart cells, bones cells, liver cells, lung cells, and blood cells circulating in the mother’s veins and arteries.[3] Retained fetal cells integrate into the mother’s tissue; they grow in number and proliferate.[4] In other words, they are living/functioning/multiplying cells.
Pregnancy involves several intricate biological processes, including the transfer of fetal cells into the mother’s bloodstream and their subsequent integration into maternal tissues, resulting in microchimerism. These chimeric cells have been reported in the liver[5], heart[6], brain[7], bone marrow[8], kidney[9], lung, and spleen.[10] Furthermore, microchimerism is the bidirectional exchange[11] of fetal and maternal cells during pregnancy. Put succinctly, Mary’s cells were in Jesus and vice versa.
Think about this: parts of the incarnate Word of God resided (and probably still reside) in Mary’s body, and vice versa. When we partake of the Eucharist, Jesus’ real presence within us is only temporary—until the accidents of bread and wine (Jesus’ body and blood) cease to be distinguishable. However, in Mary it is likely forever, because she is biologically one-flesh with her Son. The Doctrine of Concomitance informs us that Jesus’ body—even the tiniest part of it—can never be separated from the entire Jesus in his humanity and his Divinity. Could that doctrine be applicable in this circumstance? Could this be one of the reasons Mary was taken into Heaven body and soul? No part of Jesus’ body could ever be subject to cell death and decay. Does that apply in this case? If yes, what are the theological implications of that? We know that all created grace enters into creation via the incarnate Jesus.[12] Could this be part of the mystery of Mary’s being the Mediatrix of all grace?[13] I do not have those answers, but trying to answer those questions sounds intriguing.
So, what are the theological implications of that scientific fact? Jesus’s glorified body is the resurrected Temple rebuilt after three days (Jn 2:19-21). Does fetal microchimerism play into that reality in some way? The Doctrine of Concomitance says that no part of Jesus can be separated from the whole of Jesus, in Body, Blood, Soul, and Divinity. In the same way, the entire substance of a person is present in the fertilized egg, which is but a single cell. The single cell contains everything the Person will become. The fertilized egg that became Jesus was not fertilized by any sperm cell.
Science has shown that every biological mammalian life begin when the sperm penetrates the egg, causing a zinc/calcium spark of electrochemical spark of light that begins cell division. The sperm penetration is no merely coincidental to the spark, it is necessary to it. Since there was no human sperm involved in the conception of Jesus, what caused the spark? To me, the answer is obvious. It was the Holy Spirit.
Does this make Mary a member of the Mystical Body of Christ to a degree that can hardly be comprehended? Jesus is described as the Head of the Mystical Body (Eph 4: 15). According to St. Robert Bellarmine, Mary is the Neck between the Head and the Mystical Body. Coincidence [Concio xlii de Nativitate B.V.M.]?[14] When we receive Jesus in the Eucharist, does Mary become our Mother biologically and spiritually? The same can be asked about her relationship to each of us within the Mystical Body of Jesus. This post is neither the time nor place to delve deeply into the extrapolations of these scientific findings. That is a subject for later discussion.
ENDNOTES:
[1]. Boddy A, Fortunato A, Aktipis A, et al. “Fetal microchimerism and maternal health: A review and evolutionary analysis of cooperation and conflict beyond the womb.” Bioessays. 2015. Abstract can be read at: http://onlinelibrary.wiley.com/doi/10.1002/bies.201500059/abstract ; Cómitre-Mariano, B., Martínez-García, M., García-Gálvez, B., Paternina-Die, M., Desco, M., Carmona, S., & Gómez-Gaviro, M. V.. Feto-maternal microchimerism: Memories from pregnancy. iScience 25, n. 1 (2021): 103664. https://doi.org/10.1016/j.isci.2021.103664
[2]. Laura Sanders, “Children’s cells live on in mothers,” Science News, https://www.sciencenews.org/blog/growth-curve/childrens-cells-live-mothers; May 10, 2015 (accessed 04/12/2016).
[3]. Laura Sanders, “Children’s cells live on in mothers,” Science News, https://www.sciencenews.org/blog/growth-curve/childrens-cells-live-mothers; May 10, 2015 (accessed 04/12/2016).
[4]. Medical Daily, “Fetal Cells Can Be Found In A New Mother's Body And Will Effect Her Health Even After Pregnancy,” Medical Daily; http://www.medicaldaily.com/fetal-cells-can-be-found-new-mothers-body-and-will-effect-her-health-even-after-350234, Aug 28, 2015 (accessed 04/12/2016).
[5] Johnson, K. L., S. Osamu, J. Lee Nelson, W. Michael McDonnell, and D. W. Bianchi, “Significant fetal cell microchimerism in a nontransfused woman with hepatitis C: evidence of long-term survival and expansion,” Hepatology, (2002): https://doi.org/10.1053/jhep.2002.35622 ; Guettier, C., M. Sebagh, J. Buard, D. Feneux, M. Ortin-Serrano, M. Gigou, et al., “Male cell microchimerism in normal and diseased female livers from fetal life to adulthood,” Hepatology 42, no. 1 (2005): 35–43, https://doi.org/10.1002/hep.20761 ; all cited in Vicente Llorente, Marina López-Olañeta, Elena Blázquez-López, Elena Vázquez-Ogando, Magdalena Martínez-García, Javier Vaquero, Susana Carmona, Manuel Desco, Enrique Lara-Pezzi, María Victoria Gómez-Gaviro, “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” Frontiers in Cell and Developmental Biology 12 (August 2024): https://doi.org/10.3389/fcell.2024.1390533.
[6] Kara, R. J., P. Bolli, I. Karakikes, I. Matsunaga, J. Tripodi, T. Omar, et al., “Fetal cells traffic to injured maternal myocardium and undergo cardiac differentiation,” Circulation Res. 110, no. 1 (2012): 82–93, https://doi.org/10.1161/CIRCRESAHA.111.249037 ; Kara, R. J., P. Bolli, I. Matsunaga, T. Omar, P. Altman, and H. W. Chaudhry, “A mouse model for fetal maternal stem cell transfer during ischemic cardiac injury” Clin. Transl. Sci. 5, no. 4 (2012): 321–328, https://doi.org/10.1111/j.1752-8062.2012.00424.x ; Lintao, R. C. V., A. Kumar Kammala, E. Radnaa, B. Mohamed, K. L. Vincent, I. Patrikeev, et al., “Characterization of fetal microchimeric immune cells in mouse maternal hearts during physiologic and pathologic pregnancies,” Front. Cell. Dev. Biol. 11, 1256945 (2023): https://doi.org/10.3389/fcell.2023.1256945 ; all cited in Llorente, et al., “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” https://doi.org/10.3389/fcell.2024.1390533.
[7] Tan, X.-W., H. Liao, Li Sun, M. Okabe, Z.-C. Xiao, et al., “Fetal microchimerism in the maternal mouse brain: a novel population of fetal progenitor or stem cells able to cross the blood–brain barrier,” Stem Cells 23, no. 10 (2005): 1443–1452. https://doi.org/10.1634/stemcells.2004-0169 ; Chan, W. F. N., G. Cécile, T. J. Montine, J. A. Sonnen, K. A. Guthrie, and J. Lee Nelson, “Male microchimerism in the human female brain,” PLoS ONE 7, no. 9 (2012): e45592, https://doi.org/10.1371/journal.pone.0045592 ; all cited in Llorente, et al., “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” https://doi.org/10.3389/fcell.2024.1390533.
[8] O’Donoghue, K., J. Chan, J. De La Fuente, N. Kennea, A. Sandison, et al., “Microchimerism in female bone marrow and bone decades after fetal mesenchymal stem-cell trafficking in pregnancy,” Lancet 364, no. 9429 (2004): 179–182, https://doi.org/10.1016/S0140-6736(04)16631-2 ; cited in Llorente, et al., “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” https://doi.org/10.3389/fcell.2024.1390533.
[9] Florim, G. M. S., H. C. Caldas, J. C. R. de Melo, M. A. Baptista, I. M. M. Fernandes, M. Savoldi-Barbosa, et al., “Fetal microchimerism in kidney biopsies of lupus nephritis patients may Be associated with a beneficial effect,” Arthritis Res. Ther. 17, no. 1 (2015): 101, https://doi.org/10.1186/s13075-015-0615-4 ; cited in Llorente, et al., “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” https://doi.org/10.3389/fcell.2024.1390533.
[10] Rijnink, E. C., M. E. Penning, R. Wolterbeek, S. Wilhelmus, M. Zandbergen, et al., “Tissue microchimerism is increased during pregnancy: a human autopsy study,” Mol. Hum. Reprod. 21, no. 11 (2015): 857–864, https://doi.org/10.1093/molehr/gav047 ; cited in Llorente, et al., “Presence of fetal microchimerisms in the heart and effect on cardiac repair,” https://doi.org/10.3389/fcell.2024.1390533.
[11] Boddy A, Fortunato A, Aktipis A, et al. “Fetal microchimerism and maternal health: A review and evolutionary analysis of cooperation and conflict beyond the womb.” Bioessays. 2015, https://onlinelibrary.wiley.com/doi/full/10.1002/bies.201500059.
[12]. Thomas Aquinas, Summa Theologicae, III, q. 64, a. 1.
[13]. Pope Pius X, Ad Diem Illum Laetissimum, (Libreria Editrice Vaticana, February 1904), n. 14: https://w2.vatican.va/content/pius-x/en/encyclicals/documents/hf_p-x_enc_02021904_ad-diem-illum-laetissimum.html.
[14]. Fr. John Hardon, “Mystical Body,” in The Homiletic & Pastoral Review Vol. 49, n. 5, (Ignatius Press, February 1949), pp. 375-381: text can be read at https://www.catholicculture.org/culture/library/view.cfm?recnum=7520.