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Preterm delivery and intimacy during pregnancy: interaction between oral, vaginal and intestinal microbiomes

Parto pretérmino e intimidad durante el embarazo: interacciones entre los microbiomas bucal, vaginal e intestinal


During pregnancy, the microbiomes of the mouth, vagina and intestine undergo changes to adapt to the demands of the body, increasing the relationship and similarity between them. Therefore, it is pertinent to consider a literature review to determine the existence of influencing factors for a specific microbiome, which could also modify others. An example is the case of the mouth microbiome that is dependent on the intimate activities of the female, and therefore could be a factor that relates to preterm labor.


Preterm birth it is one of the principal factors that increment the mortality on children below five years, because of the increase risk for diverse diseases associated to prematurity. The increase in mortality is also secondary to repercussions on the development. The advent of a preterm newborn has being increasing since 1990 in relation with multiple causes, such as infectious diseases and dysfunction of the female reproductive organ [1].

Hypotheses and theories

During pregnancy the intestinal microbiome of the woman suffer changes in order to maintain the metabolic demands secondary to the endocrinological changes, and to facilitate the interaction of the mother’s immune system [2],[3],[4],[5]. As the vaginal microbiome continues to change through the different trimesters of pregnancy for the purpose of avoiding aggressions by pathogens; both microbiomes tend to have a growth of similar microorganisms, mostly of the lactobacillus gender. Such modifications are reversible at the end of pregnancy [2],[3].

Throughout pregnancy there’s an increment the number of bacteria in the bowel, therefore the bacterial translocation to the uterus can be a cause of preterm delivery [5].

With the changes on the intestinal and vaginal microbiome it is added a relationship of the intestinal and mouth microbiome of the mother [4]. The latter can be modified depending on the behavior and level of intimacy of the woman with its partner, an example can be the kissing activity and others. This can influence on the development and maintenance of this microbiome, finding more similitude between the microbiomes of couples than of other people [6]. Therefore, the dysbiosis of the mouth microbiome influences the development of mouth pathologies, such as caries, periodontal disease, and so would influence the advent of a preterm delivery [7].

Because of these interactions, there are different theories regarding preterm delivery and dysbiosis. Two theories are the bacterial translocation of the intestine to the uterus and the dysbiosis of the intestinal microbiome. Both theories are based on a higher number of bacteria. Then we must add the vaginal dysbiosis, which facilitates the placental infection by bacteria acquired in a retrograde manner inducing a preterm delivery, and the translocation of mouth bacteria to the placenta in mothers with periodontal disease. But these results have been contradictory [4],[5].

The dysbiosis of the diverse microbiomes with the bacterial translocation secondary to them, influence the advent of a preterm delivery through two mechanisms. First is the migration of bacteria to the placenta, this produces a subclinical localized inflammation of the region. The second is the migration of bacteria to the blood stream where a subclinical endotoxemia develops. Both processes stimulate the increase of citoquines, which generate complications through pregnancy such as the induction of a preterm delivery [5],[8],[9].

These theories are based on the interaction of the microbiomes and the changes that occur during pregnancy, together with an increased interaction between them. For this reason, the factors that influence over one of them could modify the others.


Considering the relationship of the mouth and intestinal microbiomes (the factors that influence the mouth microbiome depend on the level of intimacy of the person, and the intestinal bacterial translocation is a cause of preterm delivery); it is possible to infer that intimate activities of the mother during pregnancy (such as the presence or absence of a couple as a factor that influences the maintenance of a microbiome because of the exposition or lack of exposition to the bacteria of the couple, or a change of the couple to one not being the biological father, with a different microbiome), could be factors that produce alterations on the mother´s microbiome and immune response that influences the outcome of pregnancy.

In consequence, the absence of the fetus biological father throughout pregnancy and the level of intimacy of the mother with him or another couple could influence the advent of a preterm delivery. Therefore, it is necessary to examine the existence of such relationship.


From the editor
This article was originally submitted in Spanish and was translated into English by the author. The Journal has not copyedited this version.

Conflicts of interests
The author has completed the conflict of interests declaration form from the ICMJE, which has been translated into Spanish by Medwave, and declares not having received any funding whatsoever to write this article, nor having any conflict of interests with the matter dealt herein. The form can be requested to the author or the editorial direction of the Journal.