Richard Peet, J.D., Ph.D.
DOES A PREGNANT WOMAN’S GUT MICROBIOTA COMMUNICATE WITH HER DEVELOPING FETUS?
The Gut Microbiota during Pregnancy: How the Fetus Benefits
Does a pregnant woman’s gut microbiota communicate with her developing fetus? Yes, as biomolecules produced by bacteria in the woman’s gut are encapsulated in extracellular vesicles (EVs) that accumulate in the amniotic fluid surrounding the fetus. The EVs are ingested by the fetus. Specifically, bacteria in the mother’s large intestine or colon produce EVs. These EVs carry biomolecules, such as protein and nucleic acids, that play an important role in priming the fetus’s immune system so it will be protected after birth. The interaction between a pregnant woman’s gut microbiota and the developing fetus is another example of the beautiful and intimate interconnectedness of living organisms critical for sustaining life.
First, let’s make certain we understand the terminology we will encounter in this blog. Bacterial EVs are tiny, membrane-bound, particles that are released by bacteria into their environment. EVs play a critical role in bacterial communication, interaction with host cells, and
pathogenesis. EVs are composed of a lipid bilayer that encloses biomolecules such as proteins, nucleic acids, and metabolites. EVs transfer molecules between bacteria. In pathogenic bacteria, EVs can interact with host cells contributing to infection and immune modulation. EVs can contain DNA and RNA thereby transferring antibiotic resistance genes or other traits to other bacteria. The microorganisms that live in and on the human body are referred to as the human microbiota. These microorganisms include bacteria, viruses, fungi, archaea, and protists. The collective genomes or genetic material contained by these microorganisms is called the microbiome.
How do we know a pregnant woman’s gut microbiota communicates with her developing fetus? In a recent scientific study involving both humans and mice, researchers isolated EVs from two independent sources: pregnant women’s feces and the amniotic fluid surrounding fetuses. 1 The researchers studied the proteins and RNA contained in the EVs isolated from these two discrete locations. The profiles of proteins and RNA found in the EVs from feces and amniotic fluid were very similar indicating they had a common origin. EVs purified from the feces of pregnant women were exposed to a dye that permitted detection in the different tissues of mice. The dyed EVs were injected into the tail of pregnant mice. Within 24 hours of injection, the EVs were detected in the amniotic fluid surrounding the fetuses and in the fetuses from the pregnant mice. This experiment demonstrated that EVs isolated from a pregnant woman could travel through the blood stream of a pregnant mouse, enter amniotic fluid surrounding fetuses, and finally be ingested by the fetus itself.
Health implications for infant health. An infant is born without a gut microbiome and acquires it during birth, and after birth, though breastfeeding and contact with mom, dad, and others. A newborn needs to have an immune system that is ready to distinguish between good microbes and bad ones. It is likely mom’s EVs contain biomolecules that help prepare theinfant’s immune system for that important task. As we learn more about which gut bacteria produce EVs that transport beneficial biomolecules to the fetus, interventions can be imagined that will help mom produce, nourish, and maintain these bacteria during pregnancy.
1 Kaisanlahti et al., Maternal microbiota communicates with the fetus through microbiota-derived extracellular vesicles, Microbiome 11:249 (2023
I would like to thank my friend Michael B. Reiner, Ph,.D. for editing some of these blogs. Any errors in the blogs are solely my responsibility.