Endometrial microbiota

Under normal conditions the endometrium is colonised mainly from Lactobacilli.
Under specific conditions like immunological imbalances,(inherited or acquired) or  invasive procedures, the environment can be disturbed and a number of various abnormal populations can be developed and colonise the endometrium.

In most of the cases, especially in acute situations,  the symptoms are characteristic, and the treatment is beneficial for the woman immediately.
In some cases, the developed abnormal population is under a partial control from the immune system. This condition results in smaller numbers of newly developed bacteria, that are difficult to be diagnosed as they give very mild symptoms or are totally asymptomatic. The woman with this chronic condition will not have any obvious symptoms but it can have an adverse effect on a future pregnancy.

In case we suspect immunological imbalances and the woman suffers from repeated implantation failures, the examination of the microbiota (the asymptomatic abnormal bacterial population in the uterus) can be very useful.


1. Clinical approach to recurrent implantation failure: evidence-based evaluation of the endometrium. Harvey J. Kliman and David Frankfurter. Fertility and Sterility. Vol. 111, No. 4, p.684-693, April 2019.

2. Relevance of assessing the uterine microbiota in infertility. Moreno I and Carlos Simon. Fertility and Sterility. Vol. 110, No. 3, p.618-630, August 2018.
3. Endometriosis and the microbiome: a systematic review. M Leonardi et al. BJOG. p. 1-11. 2019.

4. Uterine Microbiota: Residents, Tourists, or Invaders. Baker M. J. et al. Frontiers in Immunology. Vol. 9, p.1-16, March 2018.

5. A pilot study and case reports on endometrial microbiota and pregnancy outcome: An analysis using 16S rRNA gene sequencing among IVF patients, and trial therapeutic intervention for dysbiotic endometrium. Koichi Kyono et al. Reproduction Medicine and Biology. 2019;18, p.72–82.

6. Selection of new Probiotics on Endometrial Health, Frontiers of Cellular and Infection Microbiology. Vol 9, April 2019.