Is the Fetus a Parasite?

3 AMAZING ways the fetus supports the mother's body

I recently found myself in the dregs of Twitter, battling prochoice arguments in which a fetus is nothing more than a “leech” or a “parasite” that lives off the mother’s body without her consent.

And while I did not take the time to respond to hecklers insisting I was a brain damaged, child abusing, nitwit, and — my favorite — rapist (someone seriously needs to sort out the biology they’re teaching in the public schools these days), I thought I’d take a moment to share my reflections here, casting my pearls before a somewhat worthier and generally kinder audience.

Photo by Souvik Banerjee on Unsplash

A Fetus Is NOT A Leech

The idea that a fetus is a leech or a parasite is based on a false analogy and a lack of scientific knowledge. These organisms are different in at least three significant ways:

• A leech or a parasite is an organism that lives on or in another organism of a different species, and benefits at the expense of the host. A fetus is an organism that lives in the same species as the mother — the very body of its mother — and benefits from the mother’s support, but also gives back to the mother in various ways.

• A leech or a parasite can be easily removed or eliminated. A fetus cannot be removed or eliminated without serious consequences for both.

• A leech or a parasite has no moral or legal rights, and no relationship with the host. A fetus has inherent moral and legal rights, and a unique and intimate relationship with the mother.

Are Fetal Mechanisms of Development Parasitic?

The leech/parasite argument implies that the fetus has no intrinsic value or dignity, and that the mother has the right to “evict” it from her womb at any time. While clearly based on a distorted and dehumanizing view of the fetus and the mother-fetus relationship, is there any truth to this argument? What exactly is the relationship between the bodies of mother and fetus? Are they truly in competition with one another, as the term “leeching” implies, or is the mother’s body organizing the development of the fetus?

As it turns out, the answer is neither. The physical relationship of pregnancy is one of mutual giving, symbiotic in nature — if lopsided.

The placenta is the organ that develops in the uterus during pregnancy to sustain fetal growth. Its DNA is identical to that of the fetus, yet shares blood supply with both mother and fetus, allowing the exchange of oxygen, nutrients, hormones, and antibodies. The placenta also filters out waste products and harmful substances from the fetus’s blood. The placenta is not a foreign or hostile entity, but a cooperative and adaptive organ that is essential for the survival and development of the fetus, as well as for the maintenance of the mother’s pregnancy. Without the placenta, there would be no fetus. And yet, the placenta also provides benefits to the mother’s health, such as passing immunity, filtering out waste, and producing hormones. The placenta is not a parasite, but a partner, that supports the mother-fetus relationship.

One of the most fascinating concepts of pregnancy is microchimerism, in which some cells from the fetus cross the placenta and enter the mother’s body, where they can integrate into various tissues and organs and remain for years — perhaps even a lifetime (meaning that Mary truly was a living tabernacle even after giving birth to Jesus). As beautiful as it is to think that pieces of my children reside with in me, it is even more fascinating that these cells act to repair maternal tissues (and may explain why women generally live longer than men). Microchimerism points not to parasitism, but is a sign of mutualism, a type of symbiotic relationship in which both partners benefit from each other.

Fetal stem cells are cells that can differentiate into various types of cells and tissues. They are pluripotent, meaning they have the potential to become any cell in the body. Fetal stem cells are abundant in the fetus and the placenta, and some of them can migrate to the mother’s body through microchimerism. There, they can act as a source of repair and regeneration for the mother’s damaged or diseased organs. For example, fetal stem cells have been found to contribute to the healing of the mother’s heart, liver, brain, and skin. Fetal stem cells can also modulate the mother’s immune system and prevent or reduce the risk of autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, and type 1 diabetes. Fetal stem cells are not invaders, but helpers, that can improve the mother’s health and well-being.

Far from being a “leech” or “parasite,” the fetus is a living, developing human being with unique DNA that deserves respect and protection. Understanding the biology of the placenta, microchimerism, and fetal stem cells reveals the complexity and beauty of the mother-fetus relationship, and the mutual benefits that they provide to each other at a physical level — just one more way that a fetus is not a burden, but a blessing, to the mother and to society.

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How do you feel about the analogy of a fetus being a leech that feeds on the mother’s blood and resources? Do you think this analogy is accurate, fair, or respectful? Why or why not?

What is the Christian response to these kinds of, ahem, dialogue on Twitter and other social media outlets?