• Dr. H. Singh, ND

How the Reproductive Microbiome Affects IVF Success Rates and risk of Recurrent Implantation Failure

Updated: Nov 22, 2021



Over the last few years we have seen a greater interest in research now evaluating the role of the microbiome on various reproductive disorders, fertility, and non-fertility related health conditions. In particular, there has been research published evaluating how the microbiome may be related to conditions like polycystic ovarian syndrome (PCOS), endometriosis, and sperm health.


In addition to the conditions listed above, there has also been research published on how the reproductive microbiome may affect chances of pregnancy with In-Vitro Fertilization (IVF) and pregnancy rates for patients with recurrent implantation failure (RIF).


Overall, we are seeing a greater importance in the role of lactobacillus spp. as they are able to prevent infections/overgrowth of other microbes without causing inflammation in the local tissue. They are able to achieve this through modulation of the pH of vaginal secretions.


A newly published study in the Journal of Clinical Medicine evaluated for correlations between the reproductive microbiome and chances of achieving a positive pregnancy test after IVF and risk of recurrent implantation failure. Overall, the sample size of the study was small with 48 patients included.


Below we will discuss two separate, yet intricately connected, microbiomes: the uterine and vaginal microbiomes. They are separated by location, however, they communicate and affect each other through vertical migration of the microbes due to their close proximity.


How does the reproductive microbiome affect IVF pregnancy rates?


The vaginal microbiome in patients that achieve a positive pregnancy with appears to favour more Lactobacillus spp. Samples collected during the luteal phase of the cycle previous to the transfer showed higher levels of lactobacillus spp. in patients that achieved a positive pregnancy test compared to patients that did not. Patients that did not have a positive pregnancy test showed higher levels of Streptococcus spp and Prevotella spp in the vaginal microbiome compared to patients that became pregnant.


In the endometrial microbiome patients that achieved a positive pregnancy test had higher levels of Lactobacillus spp., Gardnerella spp., Burkholderia spp., and Anerobacillus spp. compared to patients that did not achieve a positive pregnancy test. And patients that did not become pregnant had higher amounts of Streptococcus spp, Ralstonia spp., Prevotella spp., and Delftia spp. in the endometrial microbiome.


How does the reproductive microbiome affect risk of Recurrent Implantation Failure?


In the vaginal microbiome patients that experienced recurrent implantation failure did not have any differences in the levels of Lactobacillus spp. compared to patients that did not have RIF. Patients with RIF did, however, have higher levels of Prevotella spp., Ureaplasma spp., and Dialister spp. compared to patients without RIF.


At the endometrial microbiome level it was observed that Prevotella spp. were again elevaeted.


Also, not all Lactobacillus spp. are considered equal. Higher levels of Lactobacillus helveticus were correlated with higher RIF risk compared to patients without RIF who had higher levels of Lactobacillus iners and Lactobacillus jensenii.


Overall, it is very interesting to see how simply adjusting the microbiome may be correlated with better outcomes for patients trying to conceive. Larger studies are needed to confirm these findings, however, for patients currently trying to conceive, it is important to have a conversation regarding the reproductive microbiome, especially if you have had recurrent implantation failure, with your licensed Naturopathic Doctor.


Limitations of the study: the study had a relatively small sample size and established statistically significant correlations but the study design was unable to establish causation. Future research was suggested to closely evaluate for how the reproductive microbiome may impact chances for a positive pregnancy test and/or implantation failure risk.


This article is being shared as educational content and is in no way a replacement for medical advice or medical care, it is advised that anyone concerned about their Health should speak with their Naturopathic Doctor. Please discuss with your healtcare provider and only make changes to your medications regimen if recommended by your doctor and under their guidance.




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