What Fertility Patients Should Know About Vaginal Dysbiosis
Scientifically edited by Dr. Krystal Thomas-White, PhD
Medically reviewed by Dr. Kate McLean MD, MPH, FACOG
If you're trying to conceive, especially through IVF), you're probably familiar with hormone testing, egg quality, and embryo grading. What gets less attention is the vaginal microbiome, even though a growing body of research links it to conception, implantation, pregnancy outcomes, and even IVF success. One of the key factors researchers look at is vaginal dysbiosis, an imbalance in that microbiome. Here's what it actually is, why it matters for fertility, and what you can do about it.
What is vaginal dysbiosis?
Vaginal dysbiosis is an imbalance in the vaginal microbiome, the community of bacteria and other microbes that live in the vagina. A balanced — or "optimal" — vaginal microbiome is typically dominated by Lactobacillus bacteria, which help maintain an acidic environment (a vaginal pH below 4.5) that keeps disruptive bacteria in check.
When Lactobacillus levels drop, and other, less favorable bacteria take over — like Gardnerella, Atopobium, or Prevotella — that shift is called dysbiosis. It doesn't always cause obvious symptoms, but it's associated with conditions like bacterial vaginosis (BV), one of the most common manifestations of dysbiosis, and, increasingly, with fertility outcomes.
Dysbiosis is often picked up incidentally, if at all. Standard testing can diagnose BV, but they weren't built to give a full picture of what's actually living in the vaginal microbiome, which matters more the closer someone gets to a fertility procedure like IVF.
Symptoms of vaginal dysbiosis
Dysbiosis doesn't always announce itself. Plenty of people have an imbalanced vaginal microbiome with no symptoms at all, which is part of why it's so often missed. When symptoms do show up, the most common are:
- Unusual vaginal discharge
- A strong or "fishy" vaginal odor
- Vaginal itching or irritation
- Burning or discomfort when you pee or have sex.
These symptoms overlap heavily with several vaginal infections, which is what most people are actually being screened for when they mention any of the above to a provider.
Why vaginal dysbiosis matters for fertility
The research linking the vaginal microbiome to fertility is still developing, but the pattern so far is fairly consistent: a Lactobacillus-dominant microbiome is associated with better fertility outcomes, while dysbiosis is associated with worse outcomes.
A 2022 study following women trying to conceive naturally found that those who got pregnant within a year had higher levels of Lactobacillus, while those who didn't had higher levels of Gardnerella (a bacterium linked to BV). The connection shows up even more clearly in assisted reproduction. A meta-analysis pooling 17 studies and over 3,500 patients found that vaginal dysbiosis in IVF patients was associated with both a higher rate of early pregnancy loss and a lower clinical pregnancy rate.
Researchers are still untangling exactly how much of this comes down to the vaginal microbiome, compared with the cervical or endometrial microbiome (which are much harder to sample and usually require a biopsy). However, some studies have found that the vaginal microbiome is independently associated with fertility. Some of that overlap matters a lot for IVF specifically. Dysbiosis farther up the reproductive tract has been linked to chronic endometritis, a low-grade inflammation of the uterine lining that's been associated with lower implantation rates during embryo transfer. But there are a few potential mechanisms specific to the vaginal microbiome as well:
- Inflammation: Dysbiosis is linked to inflammatory conditions like BV, and inflammation can interfere with implantation.
- Immune response: The vaginal microbiome interacts with the immune system, which has to walk a fine line during pregnancy, protecting the body while allowing an embryo to implant and grow. Hormonal shifts during a fertility cycle can also alter the vaginal microbiome, which may add another layer to how the two systems interact during a transfer.
- STI risk: BV is associated with a higher risk of STIs, which can lead to pelvic inflammatory disease (PID) and, from there, fertility problems down the line.
- Sperm survival: Some research suggests the vaginal microbiome may affect whether sperm successfully reaches the egg, which is relevant for anyone trying to conceive naturally or doing IUI as part of their protocol.
None of this means dysbiosis directly causes infertility on its own, or that a healthy microbiome guarantees a pregnancy. But for people already navigating IVF, it's a modifiable factor worth understanding, especially compared to variables like age or egg quality.
How Evvy helps identify and treat dysbiosis
Most people find out about dysbiosis only after a BV diagnosis, or not at all, since standard OB-GYN visits don't typically screen the vaginal microbiome in detail. Evvy’s at-home Vaginal Microbiome Test uses metagenomic sequencing — a more comprehensive technology than standard in-clinic tests — to map every organism present, not just a preset list of suspects. If you’re trying to conceive, Evvy's test also includes Fertility Insights, which analyzes:
- Protective score: The beneficial bacteria that ward off infection, which could harm sperm survival
- Microbiome diversity score: The bacterial balance linked to implantation
- Fertility disruptors: The microbes associated with inflammation and BV
- STI status: Infections that can interfere with conception.
From there, Evvy connects members with providers who can interpret results and recommend treatment to help shift the microbiome toward a more protective state before a transfer.
Vaginal health is just one piece of preparing for a fertility procedure, but it's one that's often overlooked, and one you can actually act on before you get to your next transfer.
