Researchers at Imperial College London have identified shifts in the vaginal microbiome among women with obesity, suggesting a link to fertility and pregnancy outcomes. The findings appear in a recent issue of Best Practice and Research Clinical Obstetrics and Gynecology.
Within the vaginal microbiota, bacteria, viruses, and fungi mix together, but lactobacillus species are typically dominant. These bacteria produce lactic acid, helping maintain the vagina’s acidic environment. This acidity protects the female reproductive tract from infections and supports a healthy path to conception.
In the study, obese women showed more lactobacillus in the gut but less in the vagina. Metabolites from gut lactobacilli may influence the gut-brain axis, potentially complicating weight management and weight loss efforts.
Specifically, the type of lactobacilli that is common in healthy pregnancies, notably L. crispatus, was found to be markedly reduced in obese participants. This pattern has been observed across diverse populations and multiple investigations worldwide.
Moreover, the vaginal microbiota profile associated with miscarriage appeared more frequently among women who are obese. Obesity is linked to higher risks of delayed pregnancy, becoming pregnant with diminished fertility after embryo transfer, and miscarriage, particularly when assisted reproductive technologies are involved.
Weight loss and dietary adjustments were linked to a shift toward a more favorable vaginal microbiota composition. These observations hint at a possible causal relationship between body weight, microbial community structure in the vagina, and the ability to conceive. Researchers caution that any conclusions must consider ethnic background, genetic factors, and lifestyle, all of which shape the vaginal microbiome.
Beyond reproductive implications, obesity—defined as a body mass index above 30—raises the lifetime risk for several cancers and chronic diseases, including type 2 diabetes, cardiovascular disease, osteoarthritis, breast cancer, colorectal cancer, and endometrial cancer. During pregnancy, obesity can also increase the likelihood of preeclampsia and miscarriage. Some data indicate that each single point rise in BMI may lower the probability of successful implantation with assisted reproductive techniques and elevate the risk of miscarriage following embryo transfer.
A broader perspective suggests that ancient insights about gut health and nutrition may have relevance for modern approaches to supporting microbiome balance and overall immune resilience. Researchers continue to explore how imaging and science-based dietary strategies could reduce susceptibility to infections as well as support reproductive health across diverse populations.