Pregnancy and the Gut Microbiota

Adam Hassan, BSc Microbiology and Immunology
Contributor​

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Over the past few months, we, The Gut Guys, have shared with you many different implications that our gut microbiota has on our health. But have you ever wondered where these species of bacteria came from? Are you born with the bacteria that colonize your gut or do they arrive later on? And what effect do they have during the gestational (pregnancy) period?

Contrary to previous beliefs, the fetus is not a sterile environment. Microbes can be found in the amniotic fluid and a placental microbiome has been identified. Studies show that the microbiota is essential for healthy early development, pregnancy maintenance, and the first years of childhood. 

Image source: http://fertility-biocenter.com/uterine-microbiota-play-a-key-role-in-implantation-and-pregnancy-success-in-ivf-1605

As you might already know, the woman’s body undergoes several changes during pregnancy at the hormonal, immunological and metabolic levels. Physiologically, women experience weight gain, insulin resistance, glucose intolerance and low-grade inflammation (1). The microbial profiles in pregnant women are very different between the first and third trimesters. You can observe a great increase in bacteria from the Actinobacteria and Proteobacteria groups. In order to prove these differences, the microbiota from both the first and third trimesters were delivered to germ-free mice (devoid of bacteria). Mice who received ‘third-trimester’ bacteria gained weight and developed resistance to insulin as well as inflammation (2). Interestingly, diet and the intake of antibiotics are environmental factors that can influence the gut microbiota during pregnancy. Bacteroides and Staphylococcus species were shown to be more present in overweight pregnant women for example. 

Image Source: http://www.cell.com/abstract/S0092-8674(12)00829-X

Babies are born with a specific microbial profile. In fact, the gut microbiota of newborns greatly resembles the vaginal microbiota of their mothers! The vaginal microbiota is mainly dominated by species of the Lactobacillus family. These bacteria protect women and their fetus from infection. As previously mentioned in other blog posts, the harmless bacteria that colonize our bodies protect us from potential pathogens from settling and causing disease.

One fun fact is that babies have a different colonization pattern depending on the type of delivery. Babies delivered by C-section differ from vaginally-delivered infants for at least a year (3). The gut microbiota of infants changes over time. Breast-feeding favours the growth of Bifidobacteria and Lactococci and also the transmission of maternal IgA antibodies. IgA antibodies are found in mucous membranes (intestines) and these are important to control the microbiota present in the gut. Learn more about antibodies here.

So, now we’ve learned that women experience chances in their gut microbiota during pregnancy and also transfer their vaginal microbiota to their newborn infants. These babies will experience changes of their own as they grow older with diet being the main factor involved. The gut microbiota really affects us in all spheres of health and we are slowly discovering the extent of its reach. 

References
1. Nuriel-Ohayon, Meital, Hadar Neuman, and Omry Koren. "Microbial Changes during Pregnancy, Birth, and Infancy." Frontiers in Microbiology. Frontiers Media S.A., 2016. Web.
2. Koren, O., J. K. Goodrich, T. C. Cullender, A. Spor, K. Laitinen, H. K. Bäckhed, A. Gonzalez, J. J. Werner, L. T. Angenent, R. Knight, F. Bäckhed, E. Isolauri, S. Salminen, and R. E. Ley. "Host Remodeling of the Gut Microbiome and Metabolic Changes during Pregnancy." Cell. U.S. National Library of Medicine, 03 Aug. 2012. Web.
3. Neu, Josef, and Jona Rushing. "Cesarean versus Vaginal Delivery: Long Term Infant Outcomes and the Hygiene Hypothesis." Clinics in Perinatology. U.S. National Library of Medicine, June 2011. Web.