It is a fact, pregnancy leads to major endocrine, metabolic and immunological changes. However, did you know that the bacteria you harbor will also be impacted, in intestine, vagina and placenta?
Pregnancy impacts the intestinal microbiota…
The intestinal microbiota changes throughout pregnancy: the bacterial diversity as well as the richness decrease between the 1st and the 3rd trimester.
During the first trimester, the bacterial ecosystem is comparable to that of healthy non-pregnant women.
A considerable change is observable from the 2nd trimester of pregnancy, and even more important in the last trimester. These differences in composition include loss of bacterial diversity and richness. Although it is difficult to generalize disappeared species (differing from one to another), some bacterial genera are increasing, as Proteobacteria and Actinobacteria. These bacterial genera are frequently observed in people with metabolic syndrome or obesity – in particular Proteobacteria, often associated with inflammation. The intestinal microbiota of a pregnant woman is then comparable to that of an overweight person at risk of diabetes in the last trimester. These modifications are not dangerous for health in the event of pregnancy. On the contrary, they are beneficial because these phenomena are supposed to nourish and help the fetus development.
… and the vaginal microbiota…
The vaginal microbiota of women is normally dominated by Lactobacilli. This bacterial genus produces lactic acid constituting an anti-infective protection. They create an inhospitable acidic environment for pathogenic bacteria and viruses.
The vaginal microbial community varies during pregnancy. Indeed, the vaginal microbiota undergoes a loss of diversity and richness, as the intestinal microbiota does. Nevertheless, an increase in the proportion of Lactobacilli is observed, due to the hormones production. Higher production of estrogen releases more glycogen that is an energy source for Lactobacilli, but also Candida albicans, a pathogenic yeast . This explains the increased vulnerability of pregnant women to mycoses.
… as well as the placental microbiota
Far from being sterile as it has been believed for a long time, the placenta hosts a bacterial ecosystem participating in the fetus growth. This microbiota is not very diversified and rich but it could contribute to essential functions of pregnancy including more specifically immunity. The placental microbiota is mainly composed of aerobic bacteria in small quantities.
Pregnant women are experiencing many changes. Some physical ones, are easily visible, but others are not, such as the composition of microbial ecosystems. This vast army of microbes knows how to adapt in all circumstances in order to maintain the future moms and fetuses health.
KOREN O, GOODRICH JK, CULLENDER TC, SPOR A, LAITINEN K, BÄCKHED HK, GONZALEZ A, WERNER JJ, ANGENENT LT, KNIGHT R, BÄCKHED F,ISOLAURI E, SALMINEN S, LEY RE. Host remodeling of the gut microbiome and metabolic changes during pregnancy. Cell. 2012, 150(3):470-80
SEFEROVIC MD, PACE RM, CARROLL M, BELFORT B, MAJOR AM, CHU DM, RACUDIN DA, CASTRO ECC, MULDREW KL, VERSALOVIC J, AAGAARD KM. Visualization of microbes by 16S in situ hybridization in term and preterm placentas without intraamniotic infection. Am J Obstet Gynceol. 2019, 221(2):146.e1-e23