Four Facts About Fetal Microchimerism

Susana Fares Mazloum

Fetal Microchimerism

Fetal microchimerism is the confirmed presence of cells from a distinct individual in the body of a placental mammal. The placenta’s normal function is to serve as a link between the fetus and the mother, its main purpose being to exchange nutrients. In recent years, research has shown that not only nutrients can cross the placental barrier, but cells as well: both from the mother to the fetus and from the fetus to the mother (fig.1). While maternal cells can cross the placenta and end up in the fetus, research has shown that more fetal cells are transferred to the mother, resulting in a state of microchimerism. The mother will carry a small number of foreign cells that once belonged to her fetus in her body.

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Bi-directional flow of fetomaternal cells. Source: Wikimedia commons

Four facts about fetal microchimerism:

1) It was first described in 1893

Physician Georg Schmorl (fig. 2) was the first to write a paper explaining the possibility of fetal cells to cross the placenta and make their way to the mother. The paper was translated from German to English in 2007. Scientists were amazed by the details he wrote; they were similar to the confirmations we have nowadays on the issue.

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Fig.2: German physician Georg Schmorl. Source: Wikimedia Commons

2) Fetal cells can survive for decades in the mother’s organism

Many studies have reported that fetal cells can survive in the mother for decades after pregnancy. An interesting case is of a 65-year-old woman who was last pregnant with a male child 27 years before the sampling for the study. Results showed she still had fetal cells circulating in her body.

3) Fetal cells can be found in tissues and organs

Fetal cells were confirmed in various tissues and organs of mothers’ blood, skin (fig. 3), heart, lungs, lymph nodes, kidneys, livers, and, most surprisingly,  brain. In a study published in 2016, the presence of fetal cells was confirmed in the brain of 63% of 53 autopsied mothers.

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Fig.3: Fetal cells in a skin sample. Credit: Carol M. Artlett et. al

4) It has been connected to positive and negative effects

Whether fetal microchimerism has a positive or a negative impact on the mother’s health has caused an intense debate in the scientific community. Some argue that fetal cells can protect the mother from certain diseases and repair damaged organs. Others disagree, saying that microchimerism can cause autoimmune diseases and some types of cancer. Many studies were published that back both hypotheses.

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. http://doi.org/10.1002/bies.201500059

Edited by: Kaylynn Crawford and Shreya Singireddy