Vaginal Microbiome Testing and Ureaplasma, Explained

If you have been trying to conceive and feel like you have ticked every box, there is one area that often gets overlooked. It sits quietly in the background, is rarely talked about, and yet it has a real influence on whether sperm survive, whether an embryo implants, and whether a pregnancy holds. That area is your vaginal microbiome.

This is a topic I love helping women understand, because it takes something that can feel mysterious and makes it tangible. So let's walk through what the vaginal microbiome is, why it matters so much for fertility, what Ureaplasma is, and where testing fits in!

What is the vaginal microbiome?

Your vagina is home to a whole community of bacteria, and in an ideal world, that community is dominated by a group called Lactobacillus. These friendly bacteria keep the environment slightly acidic, which is exactly how it is meant to be. That acidity acts like a security system. It keeps less helpful organisms in check and creates the right conditions for conception.

When Lactobacillus levels are high and diversity is low, things tend to run smoothly. When Lactobacillus drops, and other organisms move in, we call this a state of imbalance, or dysbiosis. This is where fertility can start to be affected.

Why does your vaginal microbiome matter for fertility?

This is the part that surprises people. The research here is genuinely compelling, and it speaks to how foundational this layer of health really is.

A microbiome that is not dominated by Lactobacillus, meaning less than around 90 percent Lactobacillus, has been associated with meaningfully lower rates across several fertility outcomes. In the context of IVF, studies have linked low Lactobacillus environments with reduced implantation, lower pregnancy rates, and lower live birth rates compared with Lactobacillus dominant environments. Your microbiome is not a side character here!! It is part of the main cast! Can we please shout this from the rooftops…

It does not stop at the vagina either. The lining of the uterus has its own microbiome, and when that endometrial environment shifts away from Lactobacillus dominance, it has been associated with implantation failure and pregnancy loss.

There are a few reasons this community is so central to conception:

•       It buffers the pH of the vagina, creating an environment where sperm can survive long enough to do their job.

•       It supports healthy cervical fluid, which sperm rely on for nourishment and safe passage.

•       It helps protect the path toward implantation, supporting a uterine lining that is receptive rather than inflamed.

A few things are known to nudge the microbiome in the wrong direction. Higher body weight has been linked to reduced Lactobacillus dominance and greater diversity, both of which correlate with poorer reproductive outcomes. Douching products and sanitary items containing petrochemicals can disrupt the balance. Even cycle timing matters because the microbiome shifts throughout the month as hormones change, and again with age and after childbirth.

Where does Ureaplasma come into the picture?

Ureaplasma is one of the organisms that can show up when you screen the vaginal microbiome with a comprehensive vaginal microbiome test. It belongs to a family of tiny microbes called Mollicutes, alongside its close relative Mycoplasma. There are two main species worth knowing, Ureaplasma urealyticum and Ureaplasma parvum. FYI, you can only do this test through a functional health practitioner, such as a naturopath or nutritionist. You can request one from me here.

Okay, here is the part that causes a lot of confusion online. Ureaplasma is incredibly common. It is thought that up to 70 percent of people may carry a Ureaplasma species, and for many, it causes no problems at all. So the presence of Ureaplasma is not automatically a crisis, and it is not something to panic about.

What matters is the bigger picture. Ureaplasma is capable of causing symptoms even at seemingly low levels, and it often shows up as part of a broader imbalance, or as the thing quietly preventing that imbalance from resetting. On a microbiome profile that reports a percentage, a Ureaplasma level above around 1.5 per cent of the total microbiome may be worth paying attention to, particularly when Lactobacillus is also low.

How can Ureaplasma affect fertility?

Ureaplasma urealyticum in particular has been implicated in several reproductive concerns, including miscarriage, preterm labour, premature rupture of membranes, and low birth weight. It has also been associated with fertility difficulties, which is one reason this area attracts so much clinical interest. Ureaplasma parvum carries similar concerns in pregnancy, though it tends to be quieter outside of it.

And this is very much a conversation between both partners. In men, Ureaplasma can affect sperm. It has been associated with changes to sperm structure, reduced motility and quality, increased DNA damage, and changes to the acrosome cap, which is the part of the sperm that helps it fuse with the egg. Because partners share and influence each other's microbiomes, addressing this as a couple makes a great deal of sense.

What about Mycoplasma?

Since they travel in the same family, it is worth a quick word. Mycoplasma genitalium is now considered a sexually transmitted infection and requires medical treatment. Mycoplasma hominis is not classed as an STI, but like Ureaplasma, it can be involved in symptoms and pregnancy risk. If any of these show up on testing, they are best interpreted in the full context of your history and your microbiome as a whole, rather than in isolation.

Why test?

Vaginal microbiome testing gives us a window into all of this. It can show how Lactobacillus dominant your environment is, whether diversity is higher than we would like, and whether organisms such as ureaplasma are present and at what level.

Timing matters here. If conception is the goal, the ideal time to assess the vaginal microbiome is right before ovulation, because the environment naturally changes across your cycle. Age, whether you have had children, and your hormonal status all shape what a healthy result looks like, which is exactly why interpretation is best done with support rather than from a generic reference range.

The aim is never just to find something and remove it. The real work is in rebuilding. That means restoring pH, supporting the tissue, and repopulating with the right bacteria, so the environment can hold its balance long term rather than slipping back. A probiotic on its own rarely does the job if the underlying terrain has not been addressed.

If you take one thing away today, let it be this

Your vaginal microbiome is a quiet but genuine contributor to your fertility.

Ureaplasma is one piece of that picture, common, sometimes insignificant, but worth understanding in context, especially if you have a history of miscarriage or unexplained difficulty conceiving. Testing can bring clarity, and clarity is empowering. Instead of guessing, you get to see what is actually happening and make informed choices from there.

If this has you wondering about your own microbiome, that curiosity is a wonderful starting point. Understanding your body is one of the most supportive things you can do on the path to conception.

If this hit home for you or you are curious about how the ecology of your vaginal microbiome may be impacting your fertility, you can apply to work with me here.

References and source material

This article is written for patient education and draws on the following clinical reference material and named studies. Figures are presented for general understanding and should be verified against the original sources.

1.     Moreno, I., Codoner, F. M., Vilella, F., et al. (2016). Evidence that the endometrial microbiota has an effect on implantation success or failure. American Journal of Obstetrics & Gynecology, 215(6), 684-703. (Source of the non-Lactobacillus-dominated microbiota implantation, pregnancy, ongoing pregnancy and live birth figures.)

2.     Moreno, I., Garcia-Grau, I., Bau, D., et al. (2020). The first glimpse of the endometrial microbiota in early pregnancy. American Journal of Obstetrics & Gynecology, 222(4), 296-305.

3.     Zeng, H., He, D., Hu, L., et al. (2022). Non-Lactobacillus dominance of the vagina is associated with reduced live birth rate following IVF/ICSI: a propensity score-matched cohort study. Archives of Gynecology and Obstetrics, 305, 519-528.

4.     Graham, M. E., Herbert, W. G., Song, S. D., et al. (2021). Gut and vaginal microbiomes on steroids and women's life phases: distinct changes in hormonal milieu and vaginal microbiota.

5.     Xu, Y. P., Hu, J. M., Huang, Y. Q., & Shi, L. P. (2022). Maternal Ureaplasma exposure during pregnancy and the risk of preterm birth and BPD: a meta-analysis. Archives of Gynecology and Obstetrics, 306, 893-905.

6.     Plummer, E. L., Vodstrcil, L. A., Danielewski, J. A., et al. (2018). Combined oral and topical antimicrobial therapy for male partners of women with bacterial vaginosis. PLoS ONE, 13(1), e0190199.

7.     Lannon, S. M. R., Adams Waldorf, K. M., Fiedler, T., et al. (2019). Parallel detection of Lactobacillus and bacterial vaginosis-associated bacterial DNA in the chorioamnion and vagina.

8.     Bradfield, M. Ureaplasma species: clinical training on microbe classification, symptom thresholds (above approximately 1.5 percent of the total microbiome) and pregnancy implications.

9.     Hechtman, L. Preconception care course notes: female vaginal microbiome, pH, hormonal influence on microbiota, timing of testing and microbiome restoration strategy.