Woman’s microbiome and obstetrical and perinatal risks: what do they have in common?
Authors: Artyomenko V.V. , Mnikh L.V. , Domakova N.V. 
Published: November 2023

The article is devoted to the review of modern scientific publications about the microbiome of a woman and its importance in obstetric and perinatal practice. The composition of the microbiome is changed both in the process of human evolution and personally and in different periods of a person’s life. However, on the other hand, the microbiome is influenced by the specific environment in which a person lives. It consists of a certain collection of genomes of all microorganisms. Complications during pregnancy occur frequently, according to statistics – in every sixth pregnant woman, and pose a danger to the health of the mother and child.During pregnancy, the richness and diversity of the vaginal microbiome decreases, and different species of Lactobacillus play a dominant role. The microbiome stability is hypothesized to be associated with higher levels of estrogen concentration, absence of menstruation, and modification of cervical and vaginal fluids. During an uncomplicated pregnancy, the taxonomic composition of the vaginal microbiota remains stable with the exception of the period before labor, when there is an increase in microbial diversity. This makes the vaginal microbiome similar to that of a non-pregnant woman and is believed to be a trigger for the labor process to begin.The recent studies have determined a relationship between changes in the microbiome during pregnancy and the occurrence of complications in these women. Any change or disturbance in the microbiome balance can be involved in inflammatory processes, which can potentially have adverse effects on the course of pregnancy. A major interaction between the oral microbiome and preeclampsia involves the production of nitrogen derivatives, especially nitric oxide (NO). NO is produced from L-arginine via NO synthases (NOS), and is involved in vascular processes, especially vasodilation and tissue protection. Also, NO is indirectly involved in the processes that occur in the presence of chronic cardiovascular diseases, including hypertension and preeclampsia.In recent years, scientists have begun actively to study a correlation between changes in the gut microbiome and various nosologies regarding gestational diabetes. There is not much of this data at the moment. The gut microbiome is known to modulate insulin resistance and the inflammatory response, and changes in the microbiome may be associated with metabolic diseases. It is hypothesized that changes in the gut microbiome may lead to metabolic diseases through several mechanisms: abnormal intestinal permeability, increased absorption of lipopolysaccharide, abnormal production of short-chain fatty acids, altered conversion of primary bile acids, and enhanced production of bacterial toxins (e.g., trimethylamine-N-oxide).During full-term pregnancy, the “dynamic stability” of the vaginal microbiome is described as a higher concentration of Lactobacillus species starting at 20 weeks of gestation due to increased glycogen availability and a less complex and diverse microflora. This condition may be due to the lack of cyclical hormonal changes during pregnancy. Lactobacillus and small bacterial diversity are thought to be critical factors for the initiation of labor at the end of the pregnancy.Future therapeutic strategies are likely to be applied to modulate the composition of the microbiome, including the use of pro- and prebiotics and dietary modification. However, further research is needed to identify specific tools that can be used to develop personalized therapeutic approaches for individualized prevention and treatment.