Fertility Flora: How Friendly Bacteria Support Your Path to Parenthood

Fertility is rapidly being redefined, not just as a function of hormones, age, or genetics, but as a reflection of the intricate bacterial ecosystems within our bodies. Groundbreaking research reveals that specific communities of microbes in the gut of both men and women, reproductive tract, and uterus can significantly influence the likelihood of conception and successful pregnancy. These findings also pave the way for targeted interventions, including specialized probiotics like Pregnancy Support and Vaginal Balance by Microbiome Labs, that optimize fertility from the inside out.

The Estrogen-Gut Microbiome Axis and Female Fertility

At the center of female reproductive health lies the estrobolome, a constellation of gut microbes that metabolize estrogens via the enzyme β-glucuronidase. This process regulates the balance between active and inactive estrogen, impacting ovulation, endometrial receptivity, and conditions like endometriosis and PCOS. Gut Dysbiosis (reduced microbial diversity and imbalance) leads to diminished β-glucuronidase activity, lower circulating estrogen, and a greater risk of hormone-related infertility. Therefore, we have bacteria that produce enzymes that can limit the amount of estrogen recycling, and other bacteria produce an enzyme that contributes to estrogen dominance or excessive levels, as I will discuss below.

Hu, S., Ding, Q., Zhang, W., Kang, M., Ma, J., & Zhao, L. (2023). Gut microbial beta-glucuronidase: a vital regulator in female estrogen metabolism. Gut Microbes, 15(1).

Conversely, beta-glucosidase, another microbial enzyme, can have a disruptive effect on estrogen metabolism when its activity is elevated or unbalanced. Instead of supporting healthy estrogen regulation, excessive or misregulated beta-glucosidase activity may generate estrogen metabolites that are less biologically active, or even potentially harmful. This imbalance interferes with the normal pathways of estrogen conversion, which may contribute to either estrogen dominance or deficiency. The resulting hormonal disruption can exacerbate issues such as ovulatory dysfunction, endometrial irregularities, and ultimately hurt fertility outcomes.

By maintaining a healthy and diverse gut microbiota, balanced β-glucuronidase and beta-glucosidase activity help support optimal estrogen balance, which is critical for reproductive health. I know those two enzymes look identical, but they are slightly different. When you have an imbalance in the species that generate these, it creates an imbalance in estrogen levels, leading to irregularity in this important fertility hormone.

Nutritional choices are crucial: Western diets high in sugar and trans fats disrupt the microbial balance and hormonal pathways, while a Mediterranean-style diet rich in fiber, omega-3 fatty acids, and phytonutrients supports microbial diversity and improves fertility outcomes. Microbial metabolites such as short-chain fatty acids also regulate reproductive immunity and tissue integrity, adding another layer of control.

Microbial Species That Support or Undermine Fertility

Supportive Bacteria

Lactobacillus species (L. crispatus, L. rhamnosus, L. gasseri, L. jensenii, L. acidophilus): These dominate the healthy vaginal and endometrial microbiome, producing lactic acid to lower pH (3.8–4.5), inhibit pathogens, and reduce inflammation. High Lactobacillus abundance is correlated with higher implantation, conception, and live birth rates, while also reducing the risk of miscarriage and infection.

Bifidobacterium infantis (B. longum subsp. infantis): Key for maternal immune modulation and gut barrier health. It is also transmitted from mom to the infant during birth and breastfeeding, supporting long-term immune and neurological outcomes.

Detrimental Bacteria

Gardnerella, Ureaplasma, Chlamydia trachomatis are frequently linked to vaginal or uterine Dysbiosis, chronic inflammation, and higher rates of failed implantation or miscarriage. Furthermore, Deltaproteobacteria, Atopobium, and Sneathia can outcompete beneficial Lactobacillus and contribute to endometrial inflammation, postpartum hemorrhage, and failed assisted reproduction treatments.

When pathogenic genera dominate the vaginal or uterine community, embryo implantation rate falls and pregnancy complications rise.

Hu, S., Ding, Q., Zhang, W., Kang, M., Ma, J., & Zhao, L. (2023). Gut microbial beta-glucuronidase: a vital regulator in female estrogen metabolism. Gut Microbes, 15(1).

The Male Microbiome and the Gut–Testis Axis

Fertility in men is also intimately tied to their gut microbiome. I have worked with many clients who, by balancing the male's microbiome, we achieve conception. Through the “gut–testis axis,” gut bacteria modulate inflammation, oxidative stress, and testosterone production. Dysbiosis in men impairs androgen synthesis and spermatogenesis (making sperm), resulting in reduced sperm count, motility, and morphology. Dietary interventions and probiotic supplementation may help restore gut balance, support testosterone levels, and improve semen quality.

Microbiome Labs Probiotic Interventions for Fertility:

Pregnancy Support

This blend is specifically tailored for women from preconception to postpartum, featuring Lactobacillus strains (L. crispatus, L. rhamnosus, L. gasseri, L. jensenii, and L. acidophilus), as characterized from healthy pregnant women. It replenishes both vaginal and gut microbiota, supporting a reduction in inflammation and an increased risk of infection. Also featuring ISTILOS™ B. infantis (Bifin02™), a beneficial strain that helps establish a mutual immune balance and support the gut–brain axis for both mother and infant. These strains actively foster a microbiome profile linked to improved estrogen modulation, better embryo implantation, and reduced adverse outcomes.

Vaginal Balance

An oral probiotic supporting a Lactobacillus-dominated vaginal environment. Contains Five targeted Lactobacillus strains (L. crispatus, L. acidophilus, L. rhamnosus, L. gasseri, L. jensenii), which outcompete pathogens, regulate vaginal pH, and minimize infection risks. Along with Cranberry powder, it supports urinary tract health and further protects against pathogens. A healthy, Lactobacillus-rich vaginal environment is critical for sperm transport, optimal embryo implantation, and reduced risk of complications in natural and assisted conception.

Emerging Insights: Uterine and Systemic Microbial Crosstalk

Contrary to longstanding beliefs, the uterus is not sterile. Studies show that a Lactobacillus-dominated endometrial microbiome significantly improves in vitro fertilization rates and reduces the risk of recurrent implantation failure or pregnancy loss. Conversely, a uterine microbiome dominated by pathogens or depleted of Lactobacillus significantly diminishes the odds of embryo implantation.

These endometrial and vaginal microbial profiles often correlate, and restoring balance in both areas—potentially with targeted probiotic or prebiotic approaches—has emerged as a promising strategy for boosting fertility and reproductive success.

BiomeFx: What is your Balance?

Here at Brain and Body, we offer Microbiome Labs BiomeFx, a whole-genome sequencing characterization methodology that is sensitive and specific in bioinformatically deciphering your unique microbiome balance. As mentioned, the balance and microbial diversity of you and your partner drastically influences the hormonal and immunological components of conception, which are being understood most recently to be out-of-sight mediators of fertility. Im happy to continue my work with couples on this journey using data and targeted probiotic support to achieve these goals. Please call Brain and Body at 404-671-8499 to schedule a consult with me, Melody Bartlett. I would love to be a part of this journey!

Conclusion:

The state of the microbiomes spanning the gut, vagina, and even the uterus powerfully shapes fertility in both women and men. Microbiome-targeted interventions, such as Pregnancy Support and Vaginal Balance, are at the forefront of fertility care, helping to restore beneficial Lactobacillus and Bifidobacterium populations and crowd out pathogens. These strategies are poised to become key tools for optimizing conception, healthy pregnancy, and long-term parental and infant well-being.

As our understanding of the microbiome deepens, leveraging these bioactive microbial “matchmakers” enables a holistic, personalized, and scientifically grounded path to reproductive success.

-Melody Bartlett M.Sc.

Microbiology and Cell Science

References:

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