Researchers at the Carlos Simon Foundation have been studying how the endometrial microbiome influences fertility. Our latest research explores how obesity disrupts microbial ecosystems across multiple body sites, including the gut, oral cavity, and reproductive tract, providing insight into the fertility challenges often faced by women with obesity.
What is the Endometrial Microbiome?
The endometrial microbiome is a community of microorganisms living within the uterus. A balanced and healthy uterine ecosystem is typically dominated by Lactobacillus, a type of bacteria that helps to maintain a stable uterine environment conducive to embryo implantation. However, the disruption of this balance – a condition known as dysbiosis – can interfere with fertility by affecting uterine health and embryo implantation [1, 2].
Obesity and the Microbiome: What We Have Discovered
Obesity represents a well-known factor that can reduce fertility; however, our recent study uncovered a significant link between obesity and changes in the endometrial microbiome. We discovered a higher prevalence of microbiota dominated by Streptococcus in women with obesity, a pattern not typically observed in women with a healthy body weight [3]. Why does this matter? The presence of Streptococcus may cause endometrial inflammation, which would disrupt the conditions required for embryo implantation and early pregnancy [4] and may partially explain the poorer reproductive outcomes often observed in women with obesity.
Exploring the Connections between the Gut and Uterus
We also know that obesity affects the gut microbiota (the microorganisms living in the gastrointestinal tract), which plays a significant role in inflammation and hormone regulation throughout the body [5]. This fact raises the possibility that changes in the gut microbiome might indirectly influence endometrial function, creating a cascade of effects on fertility.
Moving Forward
Our findings clarify connections between obesity, the gut/endometrial microbiomes, and fertility. The study of these interactions aims to create a platform to develop treatments to restore uterine microbial balance, which could offer new hope for women trying to conceive, particularly those with conditions that complicate reproductive health, such as obesity.
If you want to learn more about our research, you can read the full article here!
References:
1. Moreno I, Codoñer FM, Vilella F, et al. Evidence that the endometrial microbiota has an effect on implantation success or failure. Am. J. Obstet. Gynecol. 2016;215(6):684-703. DOI:10.1016/j.ajog.2016.09.075
2. Garcia-Grau I, Simon C, Moreno I. Uterine microbiome-low biomass and high expectations. Biol. Reprod. 2019;101(6):1102-1114. DOI:10.1093/biolre/ioy257
3. Bellver J, Gonzalez-Monfort M, González S, Toson B, Labarta E, Castillón G, Mariani G, Vidal C, Giles J, Cruz F, et al. An Analysis of the Digestive and Reproductive Tract Microbiota in Infertile Women with Obesity. Int. J. Mol. Sci. 2024; 25(23):12600. DOI: 10.3390/ijms252312600
4. Baker JM, Chase DM, Herbst-Kralovetz MM. Uterine Microbiota: Residents, Tourists, or Invaders? Front. Immunol. 2018;9:208. DOI:10.3389/fimmu.2018.00208
5. King S, Osei F, Marsh C. Prevalence of Pathogenic Microbes within the Endometrium in Normal Weight vs. Obese Women with Infertility. Reproductive Medicine. 2024; 5(2):90-96. DOI: 10.3390/reprodmed5020010