The vaginal microbiome – a collection of microorganisms and their genetic components – plays a vital role in maintaining vaginal health and combating disease. 

This complex environment doesn’t remain constant and changes throughout life. Although these changes are often natural, research is continually discovering how a disruption in the vaginal microbiome impacts gynecologic and reproductive health and influences the risk for disease.  

The shifting vaginal microbiome

The vaginal microbiome is one of several microbiomes in the human body. The trillions of microbes (mostly bacteria) living in and on your body are your partners in health and wellness. You and the microbiomes that inhabit your body have a symbiotic relationship. The host (you) provides the microbes a nutritious environment to live, and the microbes return the favor by helping keep you healthy.1-3

Every microbiome needs to have the right balance of microorganisms to function well and provide protection. For example, the gut microbiome must have a rich diversity of microbiota for it to operate properly. The vaginal microbiome, on the other hand, is healthiest when it’s less diverse and dominated by the “good” bacterium Lactobacillus. Such an environment produces lactic acid, which lowers the pH level in the vagina, providing protection from adverse health conditions like bacterial vaginosis, an overgrowth of “bad” bacteria – or a yeast infection, caused by an overgrowth of Candida – a type of fungus that lives in and on the body.2-4 

Factors such as sexual activity, stress, diet, and douching can alter vaginal microbiota and change the growth environment. An imbalance (dysbiosis) in the vaginal microbiome can make you more susceptible to yeast infections, bacterial vaginosis, and sexually transmitted infections; increase your risk for endometrial cancer; and contribute to complications such as preterm birth.3,5 

Lifestyle stages affect the vaginal microbiome

Some changes in the vaginal microbiome naturally occur throughout the stages of a woman’s lifetime. The hormone estrogen is a significant player in the composition of the vaginal microbiome. Estrogen increases the amount of stored glucose, called glycogen, which promotes Lactobacillus growth. So, when estrogen levels drop, problems can arise.3 

Early childhood: It’s thought that a fetus develops within a sterile environment in the womb, and that infants get their first dose of bacteria and other microbes from their mothers during the birthing process. 

While in the womb, the mother provides the developing fetus with estrogen. After birth, however, this supply ends, and a baby’s estrogen level naturally drops. This drop causes a neutral or alkaline pH level to develop in the vagina – creating an unsuitable growth environment for Lactobacillus and an opportunity for bad bacteria to take over. Conditions such as inflammation of the vulva and vagina (vulvovaginitis) are common at young ages because the immature vaginal microbiome isn’t yet equipped to fight off bacteria.6

The vaginal microbiome of early childhood is made up of several bacteria species, including Cornebacterium spp, coagulase-negative Staphylococci, E. coli, and Mycoplasma spp. As a child gets closer to the onset of puberty, estrogen and progesterone begin to increase. This creates a more hospitable environment for the growth of Lactobacillus and the composition of the vaginal microbiome begins to resemble that of an adult.5 

Reproductive age: During menstruation, both temporary and permanent changes in the microbiome composition are more likely to occur. The diversity of the vaginal microbiome increases, the number of Lactobacillus decreases, and the overall microbiome is less stable.3-4 

The reasons for these changes can be linked to the presence of blood, using tampons, modifications to everyday hygiene routines, and sexual activity. Fluctuations in the levels of estrogen and progesterone also contribute.3 

Some evidence suggests that estrogen-only birth control promotes more Lactobacillus growth and reduces the risk of infections such as bacterial vaginosis. However, more research is needed to determine the effects of birth control on the vaginal microbiome and women’s health.3-4 

Pregnancy:  While pregnant, a woman’s sex hormones steadily increase to help maintain the pregnancy. As the pregnancy progresses, diversity in the vaginal microbiome decreases, and the concentration of the bacterium Lactobacillus increases.3 Lactobacillus inhibits an overgrowth of yeast, helping prevent vaginal yeast infections. However, since hormonal changes disrupt the pH balance of the vagina, it’s common for women to develop yeast infections while pregnant.7 

Yeast infections are most often caused by an overgrowth of Candida albicans. Although it’s possible to pass a yeast infection to an infant during delivery, infections caused by C. albicans are not associated with adverse pregnancy outcomes.8,9 On the other hand, research shows that pregnant women who develop bacterial vaginosis caused by an overgrowth of bad bacteria might have an increased risk of complications, such as preterm labor.5-6  

If you have vaginal discomfort, odor, or itching, then it’s important to consult with your obstetrician to determine which type of infection you might have to receive the correct treatment. Some commonly prescribed antifungals – such as fluconazole (Diflucan) – should be avoided while pregnant, especially during the first trimester.7 

Menopause: The vaginal microbiome also changes with hormonal fluctuations as a woman enters her menopausal years.4 When ovarian function declines and estrogen decreases, so do the vaginal secretions that contain nutrients to support healthy bacterial growth. While factors such as prior contraception use and reproductive history create some variation in the makeup of the vaginal microbiome, in general, Lactobacillus is reduced, and vaginal pH increases during the menopause years.3-4

When Lactobacillus no longer dominates the vaginal microbiome, the reproductive tract is more likely to be unbalanced, increasing the risk for infection and certain other adverse health conditions.3 For example, postmenopausal women are at an increased risk of endometrial cancer. Research shows that the microbes present in the vaginal environment of women with endometrial cancer are different from the microbes present in the vaginal environment of women who don’t have endometrial cancer.10 It's not clear, however, if the microbes were present before the cancer developed or if the vaginal microbial content changed because of the cancer. 

In addition, decreased estrogen leads to genitourinary syndrome of menopause (GSM) – a condition after menopause that affects the vagina, vulva, and lower urinary tract. When estrogen decreases, it leads to changes in the anatomy and function of these tissues, causing symptoms such as vulvovaginal discomfort or pain and urinary issues. GSM further changes the acidic environment of the vagina, increasing the risk of contracting infections for menopausal and postmenopausal women.11 

Manipulating the microbiome: The future of medicine? 

An increasing number of studies are examining the links between the vaginal microbiome and health, including a current 2022 study that is evaluating the effectiveness of transplanting vaginal fluid from one woman to another to alter the vaginal microbiome and prevent bacterial vaginosis.12 

Unraveling the cause and effect of an unhealthy microbiome is highly complex. Manipulating this intricate ecosystem could one day help improve health, prevent or treat disease, and transform patient care. As the scientific world expands its knowledge about the microorganisms that inhabit the human body, new insights will lead to new approaches of treating disease and improving health and well-being. 

A word from Thorne

Thorne offers a wide range of nutritional supplements for all phases of a woman’s life. Look for a probiotic supplement especially formulated for maintaining a healthy vaginal microbiome – coming in early 2023.

References

  1. Thursby E, Juge N. Introduction to the human gut microbiota. Biochem J 2017; 474:1823.
  2. Giampaolino P, Foreste V, Di Filippo C, et al. Microbiome and PCOS: state-of-art and future aspects. Int J Mol Sci 2021;22(4):2048.
  3. Chen X, Lu Y, Chen T, et al. The female vaginal microbiome in health and bacterial vaginosis. Front Cell Infect Microbiol 2021;11:631972.
  4. Graham ME, Herbert WG, SD Song, et al. Gut and vaginal microbiomes on steroids: implications for women’s health. Trends Endocrinol Metab 2021;32(8):554-565.
  5. Auriemma RS, Scairati R, Del Vecchio G, et al. The vaginal microbiome: a long urogenital colonization throughout woman life. Front Cell Infect Microbiol. 2021;11:686167
  6. Verstraelen H, Vieira-Baptista P, De Seta F, et al. The vaginal microbiome: I. research development, lexicon, defining "normal" and the dynamics throughout women's lives. J Low Genit Tract Dis. 2022;26(1):73-78. 
  7. Yeast infection during pregnancy. Over-the-counter treatment OK? Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/vaginitis/expert-answers/yeast-infection-during-pregnancy/faq-20058355 [Accessed November 3, 2022]
  8. Yeast infection (vaginal). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/yeast-infection/symptoms-causes/syc-20378999 [Accessed November 3, 2022]
  9. Sobel, J. Bacterial vaginosis. UpToDate. https://www.uptodate.com/contents/search. [Accessed November 3, 2022]
  10. Walther-António MR, Chen J, Multinu F, et al. Potential contribution of the uterine microbiome in the development of endometrial cancer. Genome Med 2016;8(1):122. 
  11. Angelou K, Grigoriadis T, Diakosavvas M, et al. The genitourinary syndrome of menopause: an overview of the recent Data. Cureus. 2020;12(4):e7586.
  12. Pioneering research to modify vaginal microbiome and treat bacterial vaginosis. Massachusetts General Hospital. https://advances.massgeneral.org/obgyn/article.aspx?id=1489 [Accessed November 13, 2022]