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The (un)Healthy Vagina: The Role of Hormones  

April 4, 2024 . dija

Welcome to the wonderful world of the vagina, where a self-contained environment of bacteria, yeasts and fungi protects you. Most people know very little about vaginal health, while a deficiency of certain bacteria in the vagina increase the risk of bladder infections, fungal infections, premature births, infertility and STIs. Currently, scientists worldwide are studying the intricacies of vaginal health and its maintenance. In this place, we will teach you everything you need to know about this in the next six months.  

Today in part two: what do your hormones have to do with your vaginal health? (Read part one first before reading on!)  

The big question that’s probably on your mind, as well as mine, since finding out about the vaginal microbiome is: How can I find out more about my own vaginal microbiome? Do I have enough lactic acid bacteria? Is my vagina ‘healthy’, per say?   

Answering that last question isn’t as simple as it might seem. A vagina with high acidity, a wide range of diverse bacteria, but few lactobacilli is often less resistant to certain health issues. However, this does not necessarily mean that you’ll experience symptoms. So then, would you call a vagina as such ‘healthy’ or ‘unhealthy’?   

Some companies, like Evvy, already provide tests where you can easily take a vaginal swab at home, send it off, and get your microbiome analysed. However, as of now, these services are only accessible in the United States. But of course, the results from these tests are most valuable when there’s a corresponding treatment method available. For example, bacterial vaginosis can be treated with antibiotics prescribed by a doctor. However, this is where science is still not entirely clear: what kind of treatment helps with which microbiome-profiles? 

Even if you don’t have a (home) test kit, you can still learn more about your microbiome. Your hormone levels can also provide valuable clues.  

A Dynamic Girl

Just a quick refresher: every vagina has its own special mix of bacteria, fungi, and yeast, known as the microbiome, which can impact your health. If you’re lacking in lactobacillus, for instance, you might be more prone to infections and inflammation. Additionally, a lactobacillus deficiency is also connected to fertility problems and menopause issues.  

Everyone’s vaginal microbiome is unique, but it does change with time. Whether you’re five years old, fifteen, or sixty-five, the bacteria present look vastly different. What’s more, within the span of just a month, the composition can also undergo changes. That dynamic is largely determined by hormones. So, the big changes in hormones during life stages – like puberty, pregnancy, and menopause – have a profound effect on the vaginal microbiome, especially in how much lactic acid bacteria, like lactobacillus crispatus, are around. Estrogen, the sex hormone, seems to be especially powerful in influencing the vaginal microbiome. 

Since I’m in my fertile years at 33, I likely have more lactic acid bacteria compared to my 63-year-old mother and my 2-year-old daughter. My mother’s estrogen production has slowed down since she’s reached menopause, while my daughter’s ovaries haven’t started producing estrogen yet. So, if we ignore individual peculiarities, we can assume that I probably have the highest amount of lactobacilli among us.  

Between Puberty and Menopause 

Your menstrual cycle, in addition to your age, can provide insights into the composition of your vaginal microbiome. This is because the menstrual cycle influeces your estrogen levels. During the first part of your cycle, from bleeding to ovulation, estrogen is highest as it stimulates egg growth. In the second part, from ovulation to bleeding, progesterone becomes the dominant hormone.  

A Canadian study of healthy women found that the microbiome remained relatively stable in most menstrual cycli. Only in those who are more susceptible to an imbalance, the number of disruptive bacteria increased during their menstruation, making them more susceptible to infections at that time. These people may therefore suffer from bacterial vaginosis immediately after their menstruation. 

The Isala research project in Belgium also discovered that the vaginal microbiome tends to be more diverse in women just after their periods. This means that during this time, there’s a wider variety of bacteria present, including several types of lactic acid bacteria. Researchers are currently delving deeper into how the menstrual cycle impacts bacterial composition. They suspect that bacteria like Lactobacillus jensenii and Gardnerella might be attracted to iron, which is naturally found in (menstrual) blood. So, during your period, these bacteria thrive to protect your vagina, leading to their increased presence in the week after menstruation. Additionally, the bacterium Lactobacillus iners appears to be more abundant during this time. Further on in the menstrual cycle, the vaginal microbiome seems less diverse, but the crispatus bacteria do seem to be present in more significant numbers, which makes you less susceptible to the health issues discussed earlier on.  

So, based on this information, I can probably make a guess about my own vaginal microbiome right now. Since I’m in the third week of my menstrual cycle, it’s likely that I have fewer types of bacteria, but I probably have a good amount of lactobacillus crispatus.  

The Menopause

As estrogen levels drop, the acidity in the vagina goes up – allowing other types of bacteria more opportunities to grow. In menopausal women, there’s often a decrease in lactic acid bacteria and in increase in other types like Prevotella and Anaerococcus. This doesn’t mean you’re instantly unhealthy, but it does make you more susceptive to issues, and you can adjust your lifestyle accordingly – more on that in the next blog! 

It’s quite ironic: menopause is accompanied by a drop in estrogen levels, leading to fewer lactic acid bacteria in the vagina. Interestingly, a low count of these bacteria is associated with more menopause symptoms. So, it’s a bit of a chicken-and-egg situation: is the low presence of lactic acid bacteria a hallmark of menopause symptoms or the cause? That question remains unanswered. What researchers have observed is that women who received extra estrogen during menopause saw an increase in Lactobacillus, and they experiened fewer symptoms as a result. 


During pregnancy, women often have a lot of Lactobacillus crispatus bacteria in their vaginal microbiome. This is probably because their bodies product a lot of estrogen during those nine months. Even though their microbiome migh thave fewer types of bacteria, this actually makes them more resistant to certain problems.  

However, what they discovered at Isala in Belgium is that in individuals who have been pregnant – and this also applies to people who have had a stillbirth or abortion – the presence of lactobacillus crispatus is lower compared to women who haven’t had children or been pregnant. Instead, higher levels of Bifidobacterium and Stretococcus were observed in women with children. But what that exactly means, they don’t know yet. It’s a bit unsatisfying, huh? 

Either way, it’s great for babies born via vaginal delivery to carry those vaginal bacteria with them. Those make up the microbiome on their skin, mouth, intestines, and upper respiratory tract for the first period. For babies who were delivered via cesaerean section, you can still see noticeable differences in their gut microbiome even years later. 

Next Month

33 years ago I had my mother’s vaginal microbiome on my cheeks, now I have less crispatus myself because of my pregnancy. These are all wondrous facts beyond my control.   

Next month I’ll dive into the more day-to-day: how does my lifestyle affect my vaginal microbiome? Also, do I have any influence on the health of my vagina? 

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