How Your Reproductive Microbiome Affects Your Fertility: Why the Bacteria in Your Vagina Matter

Our body’s microbiome ideally functions as part of our immune defenses, which is composed of bacterial ‘good guys’ that protect us from foreign invaders. 

Image: CDC via Unsplash

These bacteria reside everywhere in our body, including our reproductive tract. Lactobacilli are the predominant normal type and are important because they produce hydrogen peroxide and lactic acid, which decrease vaginal pH. I think of this as akin to a Florida summer — you’d probably avoid it in favor of a time when the environment was more hospitable. And it’s safe to say it’s sweltering: a whopping 9% of the entire body’s bacterial load is in the vagina. 

A strong reproductive microbiome may help optimize fertility and lower miscarriage. 

A Lactobacilli-dominant reproductive environment has been associated with higher pregnancy rates. 

On the flip side, dysbiosis (a fancy way of saying an imbalance in the microbiome) has been associated with: 

This may be mediated through bacterial vaginosis (BV), which is the most common form of abnormal microbiome and is made up of anaerobes that overrun the Lactobacilli. BV then produces amino compounds that increase the vaginal pH. A vicious cycle is born that favors continued BV growth and Lactobacilli suppression.

We know bacterial vaginosis can be associated with negative pregnancy outcomes, including miscarriage and preterm birth. 

What happens to the reproductive microbiome in infertility?

Image: CDC via Unsplash

Women with infertility may have a different microbiome in their reproductive tract compared with fertile women. 

In women who have infertility, those who get pregnant with IVF may have different microbiomes than those who don’t. 

One study examined the bacteria on the embryo transfer catheter tip and found that non-Lactobacilli-dominant microbiota was associated with negative impacts on implantation, term birth rate, and miscarriage. 

So what can be done about this?

Image: Lex Guerra on Unsplash

Environmental factors may influence the microbiome. This means good hygiene, don’t douche (it’ll change the pH), and avoid smoking.

The data looking at whether probiotics changes outcomes is still emerging, but they are typically so well-tolerated that I think it is a great option. Remember that the reproductive microbiome is unique so you must find one that has the correct type of bacteria. This is different than the typical bacteria seen in the gut (and thus, the majority of probiotics on the market).  

Lactobacilli crispatus, jensenaii, gasseri, and iners have been reported to be predominant in the vagina. 

Prebiotics (nutrients that are needed for the good bacteria) like lactoferrin may also be helpful but there needs to be more studies looking at this. 

Antibiotics are somewhat controversial but may help reset the microbiome, especially in the setting of chronic endometritis. 

New testing is on the horizon using a sample of tissue from the uterine lining and analyzing it for a specific woman’s microbiome.  

Inquire with your doctor whether you may be a candidate for these options! And if you’re trying to conceive, check out these posts to arm yourself with info. Because the brain is part of our defense system, too.


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