By: 6 March 2020
First glimpse of endometrial microbiota during pregnancy

A team of Valencia University (UV), in collaboration with the Igenomix Foundation and the INCLIVA, has managed to access the human endometrial microbiota during early pregnancy.

The result, published in the Americal Journal of Obstetrics & Gynecology, shows that the uterus is dominated by Lactobacillus and provides the first profile of a pregnant woman’s microbiota.

American Journal of Obstetrics & Gynecology (ELSEVIER) has published in its most recent number “The first glimpse of the endometrial microbiota in early pregnancy”, research that comes from the collaboration between the UV, the Igenomix Foundation and INCLIVA. The work reveals an historical landmark for women’s reproductive health with the access, for the first time, to the endometrial microbiota during early pregnancy, whose evolution led to the birth of a healthy baby.

“This could be the starting point to learn the interaction between the microbes and the beginning of human life,” explain project head Carlos Simón – professor in Paediatrics, Obstetrics and Gynaecology for the UV – and Inmaculada Moreno, researcher for the Igenomix Foundation and first signee of the article.

Even though microbes have always been linked to infectious diseases, humans also live surrounded by beneficial bacteria called commensal bacteria, which are part of their organism and contribute to their vital functions. In a person’s body there are ten times more microorganisms than their own cells. Until recently, it was believed that the uterus was a sterile cavity that bacteria had not reached, as it had to hold the foetus during pregnancy.

The microbial profile of the endometrium (the mucosal layer that lines the uterine cavity) has been described recently. “We know that the endometrium is populated by two types of microbial profiles: the ‘Lactobacillus-dominant (LD)’ one and the ‘non-Lactobacillus-dominant (NLD)’ one because there are other pathogenic bacteria. The latter is linked to a lower rate of pregnancies and a higher rate of abortions,” explains Inmaculada Moreno. “However, we did not know the relevance of this endometrial flora during pregnancy, as this type of studies had always been conducted at moments prior to gestation,” adds the researcher.

“A casual finding allowed us to study her endometrial microbiota when the patient had been pregnant for four weeks. That is when we happened to obtain the first microbial profile of a pregnant women whose gestation process was successful,” says Carlos Simón, who is also at the head of the scientific advisory board of the Igenomix Foundation.

“This information allows us to learn something more about the beginning of life, as it is this microbial surrounding where the pregnancy took place successfully. This result is now the starting point for future studies that will attempt to determine how to prepare the endometrial flora to achieve reproductive success,” concludes Inmaculada Moreno.


Reference: The first glimpse of the endometrial microbiota in early pregnancy. Inmaculada Moreno, Iolanda Garcia-Grau, Davide BAU, David Perez-Villaroya, Marta Gonzalez-Monfort, Felipe Vilella, Roberto Romero, Carlos Simon. DOI:

Source: Valencia University