In this article Dr. Ros discusses probiotic treatments when the microbiota is altered in women, such as in cases of repeated miscarriages and/or implantation failure. The relationship between fertility, the microbiota and the use of probiotics is a subject that is currently under debate and study.
What is the microbiota?
The microbiota is the set of microorganisms, i.e. bacteria, viruses, fungi, archaea and protists that live in the human body. On the other hand, the microbiome is broader, encompassing the whole of the microbial communities, including genes and metabolites, as well as the environmental conditions that surround them.
In this case, bacteria act as an ecosystem, coexisting in the human body in equilibrium without causing pathology, and even helping us to be healthy on some occasions. The moment the balance in the microbial flora is broken, a disease may originate.
In recent times, thanks to advances in genetic techniques, it has been possible to discover the existence of these microorganisms in different organs of the body that we previously thought were sterile, as is the case of the female and male reproductive system.
The microbiota of the vagina and the endometrium are different, with lactobacillus being the dominant bacterium when they are healthy. The activity of the microbiota in the vagina is known, and lactobacillus – the dominant bacterium in this ecosystem – metabolizes sugars generating lactic acid.
In the case of the endometrium, a 90% Lactobacillus-dominated microbiota is considered to be a predictor of reproductive success, although a non-Lactobacillus-dominated microbiome may be normal in some patients.
It should not be forgotten that there is also a microbiome in the rest of the reproductive tract, for example in the fallopian tubes, the follicles of the ovary in the male reproductive tract that can affect the development of some sex cells.
Does the microbiota affect endometrial receptivity and pregnancy?
The presence of bacteria other than lactobacillus in the endometrium may be the origin of some implantation and/or miscarriage failures.
Can the microbiota be modified?
Our microbiota is influenced by different factors, such as age, pregnancy, sexual activity, smoking, exogenous hormones, stress, food, environment, the use of some antibiotics and even by the microbiota of our partners. It can be improved with probiotic foods or a healthier diet.
Estrogen levels vary depending on the timing of the menstrual cycle and affect the vaginal microbiota, as well as probably the endometrial.
Do assisted reproductive techniques affect the vaginal microbiota?
The success of embryo transfer varies depending on several factors, including the presence of microbial colonization of the upper genital tract.
Some studies and research have shown that the clinical pregnancy rate is higher in transfer in the group of patients with no microbial growth compared to the group in which cultures were positive for microbial colonization.
The specialist physician will be very careful to reduce the risk of microbial contamination during embryo transfer by cleaning the external os of the cervix and also avoiding touching the vaginal and external walls of the cervix with the end of the catheter.
During ovarian stimulation there is a major change in circulating hormones that have a major impact on microbiotic changes related to pregnancy outcomes.
Does semen have a microbiota?
The answer is yes. Semen contains microorganisms along with other elements, such as proteins and/or inflammatory factors. Therefore, semen is a medium for the transmission of microorganisms between women and men, although to date it has been less studied than the female genital microbiota.
How do probiotics improve fertility?
In recent times, various benefits of probiotics have become known for pregnancy and these benefits are potentially exploited in reproductive health.
Thus, probiotic supplements have become an object of research, and lactobacillus rhamnosus has demonstrated its ability to restore vaginal flora in up to 82% of women with a history of dysbiosis. Probiotics containing this bacterium can be used over a long period of time as an alternative to antibiotics, especially in cases of high rates of infection recurrence.
Nowadays, the latest research indicates that having a normal vaginal flora may be related to an adequate endometrial flora, since the bacteria that colonize the endometrium most commonly colonize upward from the vagina.
For more information, please consult with an Assisted Reproduction Specialist.