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Exploring the Microbiome

The Maternal Microbiome Explained

deborah slobada
deborah slobada
Deborah Sloboda

Deborah Sloboda

Professor and Canada Research Chair in Perinatal Programming
Dept. of Biochemistry and Biomedical Sciences, McMaster University

Kate Kennedy

Kate Kennedy

PhD Candidate
Dept. of Biochemistry and Biomedical Sciences, McMaster University

What is the maternal microbiome?

Earth’s biosphere is made up of different types of “biomes” (Tropical Rainforest, Desert, Grassland, etc.), communities of living organisms—plants and animals—and the climate that they share. As humans, our micro-biomes (gut microbiome, skin microbiome, etc.) are communities of microorganisms—bacteria, fungi, and viruses— and the environment that they share on our bodies. Our microbiomes protect us from pathogens, help us extract nutrients from our food and maintain a healthy immune system. The maternal microbiomes—the gut, skin, and vaginal microbiomes of a pregnant person—are usually the first microbes that we are exposed to during and after birth.

Does the intrauterine environment have the capacity to shape health well beyond fetal life?

Our health is influenced by genetics (nature) and our environment (nurture), but the impact of our environment starts earlier than you think! In fact, our early life environment —before we are born—has the greatest impact on our health (and disease risk) because of how quickly we are growing and developing. This life course approach to understanding health and disease spans the period before conception (aka eggs and sperm), into embryonic and fetal life, and is based upon the fact that early developmental adaptations modify how we will respond to our postnatal environment. Known as the Developmental Origins of Health and Disease; we now know that our early life environment is associated with diseases that we used to call “lifestyle associated diseases” like diabetes and obesity. This concept heightens the importance of being healthy before conception, as well as throughout pregnancy and lactation, so that babies are not only born healthy but stay healthy throughout their adult life. It also highlights the fact that health and disease risk can be passed across generations: a poor start to life leads to disease during adulthood, including during pregnancy again, perpetuating a cycle of disease risk. This is also why we advocate for health equity across our communities, to ensure that everyone has a healthy start to life.

Is it true that early-life colonization with specific microbes can predict health outcomes? (Asthma? Obesity? Any others?)

Our gut microbiota plays an important role in shaping our metabolic and immune development. This may be why environmental factors that change our early-life microbiota composition (antibiotic use, C-section delivery, bottle feeding) have been linked to changes in our risk of asthma1 and obesity2,3 later in life. But it’s important to remember that these microbes need an environment to thrive in (that is, our intestines). So, it’s likely that it is the interaction between how intestines grow and our development (as an embryo or fetus or neonate) plus the microbes that live there that influences health outcomes, but there is still a lot we don’t know about our relationship with our microbes.

When does microbial colonization occur?

In healthy pregnancy, without intrauterine infection, the current evidence (including our own) suggests that babies don’t have a microbiome before birth. This means that we are first exposed to our mother’s microbiome during delivery and that microbial colonization happens during and after birth.

Microbiome research has come a long way, how have current technologies affected the outcomes of your study?

The explosion of microbiome research over the past 20 years has been driven by advances in DNA sequencing technology. The increasing accessibility of DNA sequencing has vastly increased what we know about human microbiomes but has also sparked controversies. One such controversy surrounds the existence—or lack thereof—of in utero colonization (fetal and placental microbiomes). Our study found that colonization does not occur before birth and shows the importance of applying robust experimental methods (including the appropriate controls for contamination) when using DNA sequencing for microbiome research. But this is the great thing about science – it’s always advancing and collectively scientists are always improving our use of new technologies to make our results reproducible and robust!

1.Pettersen, V. K. & Arrieta, M.-C. Host-microbiome intestinal interactions during early life: considerations for atopy and asthma development. Curr. Opin. Allergy Clin. Immunol. 20, 138–148 (2020).
2.Baron, R. et al. The relationship of prenatal and infant antibiotic exposure with childhood overweight and obesity: a systematic review. J. Dev. Orig. Health Dis. 11, 1–15 (2019).
3.Wilkins, A. T. & Reimer, R. A. Obesity, early life gut Microbiota, and antibiotics. Microorganisms 9, 413 (2021).

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