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The First Glimpse of the Endometrial Microbiota in Early Pregnancy

Written by
Dr Fathalla Ali, PHD Paediatrics


A research team from the Universitat de València, in collaboration with the Igenomix Foundation and INCLIVA, for the first time has managed to describe the structure and function of human endometrial (the mucous layer that lines the uterine cavity) microbiota in a woman before an embryo transfer that lead to spontaneous abortion and during the 4th week of gestation in the same women who subsequently had a successful pregnancy.

  • They found that, the microbiota profile of endometrial fluid collected before the spontaneous abortion showed a non-Lactobacillus-dominant microbiota whereas, the microbiota profile in the sample obtained at the 4th week of the successful pregnancy in the same women showed a Lactobacillus-dominant microbiota.
  • The functional metagenomic analysis showed that, 2 different Lactobacillus species were identified which are L. iners and L. crispatus. L. iners has been known by its defence mechanism and basal function such as energy production and cell division.
  • These species were found to be the dominant microbes in the endometrium collected at the 4th week of the early successful pregnancy.
  • On the other hand, L. crispatus along with other non-Lactobacillus spp. were found to be dominant in the endometrium collected before spontaneous abortion.
  • Authors concluded that, this findings could highlight the emerging relevance of commensal bacteria in the endometrium, facilitate understanding the cause of first-trimester spontaneous abortion, help to develop a diagnostic tools and lastly, establish the basis for using microbiota intervention as alternative and personalised therapeutic procedures.

Keywords: microbiota, pregnancy, endometrial


Moreno, I., Garcia-Grau, I., Bau, D., Perez-Villaroya, D., Gonzalez-Monfort, M., Vilella, F., Romero, R., & Simón, C. (2020). The first glimpse of the endometrial microbiota in early pregnancy. American journal of obstetrics and gynecology, 222(4), 296–305. Click here.

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