Fertility and the Microbiome

Written by Clare Carrick ANutr (BHSc Nutrition and Health Promotion) 
Scientifically reviewed by Dr Fathalla Ali, PhD (Paediatrics)  :  23/12/2021

Full article : https://www.mothersbabies.org/fertility-and-the-microbiome/

Most of the time, when you hear the word ‘microbiome’, it’s in relation to the gut microbiome, where so much of the research has been focused. But recently, discussion of numerous other microbiome that exist on and in the body are receiving more attention. These include the microbiome of the vagina, semen, uterus, and follicular fluid, and research has shown that each of these might play a part in how easily you fall pregnant, and your chances of reaching full term once pregnant (1). 

What is a Microbiome?

The term microbiome describes the group of bacteria, viruses, fungi, yeast and archaea that live together, hopefully harmoniously, in various parts of our body, including the gut, mouth, skin, and vagina (1). The composition of the microbiome (i.e. the strains of microbes that are present), and the balance between these different microbes are important because they impact many aspects of the woman’s health, including her chances of successfully conceiving (1). 

Pregnancy and the Microbiome

Pregnancy brings about a whole host of changes to a woman’s body, including alterations to the existing microbiome, as well as the development of new microbiome within the placenta and the fetus (1). Although the ideal microbiome composition for optimising fertility and sustaining a healthy pregnancy has not been fully determined, there are certain patterns developing in the research that may help to shed some light on some of the traits that seem to support optimal fertility (2, 3, 4, 5, 6).

Is Lactobacillus the key?

Having more of the strain of bacteria known as Lactobacillus in the uterine microbiome has been associated with better chances of falling pregnant, sustaining the pregnancy to full term, and delivering a healthy baby (2). This is also the same for the vaginal microbiome, where a Lactobacillus-dominant microbiome has been shown to result more often in a successful pregnancy (3). It is important to note, however, the definition of a ‘healthy’ microbiome varies between women, age, and ethnicity, and so, it’s not a ‘one-size-fits-all’ approach when it comes to our microbiomes (4).

IVF Success

Research on the microbiome within follicular fluid (the fluid surrounding the egg) shows that the microbes here may also have an impact on the likelihood of successful IVF transfers (5). Again, an abundance of the Lactobacillus strain has been linked to an increased success rate for IVF (5). It also seems that some less desirable microbes (pathogens) can reside in follicular fluid, and that, if they do, there’s a higher chance of failed implantation (5). 

Men Matter Too!

Studies have again shown that a microbiome with plenty of the Lactobacillus strain, in this case the microbiome of the semen, is a sign of healthy semen (6). Of course, there are other potential causes for low quality semen, such as genetics, but the exciting thing about learning more about your microbiome composition is that it is modifiable, as opposed to genetics, which are set in stone (6).

What Does This All Mean For You?

Microbiome are effected by many external factors, some of which you may be able to optimise with a few small lifestyle changes or choices along the way. What you choose to eat has a huge impact on the composition of your microbiome, and can have a significant effect on reproductive success (1). Dietary intervention is something that you can implement prior to trying to have a baby to give yourselves the best chance for a healthy pregnancy (1). A health professional can help you consume more lactobacillus-promoting foods. The use of pre- and probiotics pre-conception and during pregnancy is also an area that offers promise to support healthy microbiome for conception, as well as avoiding the unnecessary use of antibiotics if possible (1).

Keywords: Fertility, Microbiome, Pregnancy, Lactobacillus


  1. Schoenmakers, S., Steegers-Theunissen, R., & Faas, M. (2019). The matter of the reproductive microbiome. Obstetric medicine12(3), 107–115. 
  2. Moreno, I., Codoñer, F. M., Vilella, F., Valbuena, D., Martinez-Blanch, J. F., Jimenez-Almazán, J., Alonso, R., Alamá, P., Remohí, J., Pellicer, A., Ramon, D., & Simon, C. (2016). Evidence that the endometrial microbiota has an effect on implantation success or failure. American journal of obstetrics and gynecology215(6), 684–703. 
  3. Hyman, R. W., Herndon, C. N., Jiang, H., Palm, C., Fukushima, M., Bernstein, D., Vo, K. C., Zelenko, Z., Davis, R. W., & Giudice, L. C. (2012). The dynamics of the vaginal microbiome during infertility therapy with in vitro fertilization-embryo transfer. Journal of assisted reproduction and genetics29(2), 105–115. 
  4. Power, M. L., Quaglieri, C., & Schulkin, J. (2017). Reproductive Microbiomes: A New Thread in the Microbial Network. Reproductive sciences (Thousand Oaks, Calif.)24(11), 1482–1492.
  5. Pelzer, E. S., Allan, J. A., Waterhouse, M. A., Ross, T., Beagley, K. W., & Knox, C. L. (2013). Microorganisms within human follicular fluid: effects on IVF. PloS one8(3), e59062. 
  6. Weng, S. L., Chiu, C. M., Lin, F. M., Huang, W. C., Liang, C., Yang, T., Yang, T. L., Liu, C. Y., Wu, W. Y., Chang, Y. A., Chang, T. H., & Huang, H. D. (2014). Bacterial communities in semen from men of infertile couples: metagenomic sequencing reveals relationships of seminal microbiota to semen quality. PloS one9(10), e110152. 

From: MotherBabies.org