VAGINAL MICROBIA AND NORMAL DELIVERY

   The gene package provided by the microorganisms or microbiota living in the human body is known as the human microbiome. It has been determined that microorganisms, which are thought to be dangerous invaders, provide critical functions in basic human processes and that there are non-pathogenic microorganisms in many body fluids and anatomical regions that are considered sterile. Colonization of microbiota is a process that starts from the intrauterine period and continues by increasing its diversity especially up to the age of three. Therefore, it is important to know the factors affecting the colonization of the microbiota from the intrauterine period. One of these factors is the maternal vagina. Impaired maternal vaginal microbiota may cause pregnancy complications and preterm delivery. In addition, the mode of delivery has a significant effect on the development of the microbiota in the fetus. Microbiota transition during pregnancy and birth continues with postpartum breastfeeding. It is necessary to know the effects of pregnancy, childbirth and breastfeeding on the microbiota and to raise awareness of health professionals and expectant mothers about the factors that negatively affect the formation of healthy microbiota in these processes. The human microbiome plays a role in maintaining health, but it is also thought that certain changes in microbial species adversely affect maternal and child health. Microbiota development begins in the uterine environment, but it has been shown that factors such as mode of delivery, vaginal environment, antibiotic and probiotic use during pregnancy, and lifestyle affect the initial colonization process of the newborn microbiome. With recent studies, it is thought that microbial colonization, which occurs from the first years of life, affects the disease/health status of women in all periods of their life.

Relationship of Birth Type with Microbiota

  As newborn babies pass through the birth canal, they are exposed to the vagina's ecosystem, which is densely colonized by a wide variety of microorganisms. Studies show that there is an interaction between the gut microbiome and the immune system (gut-associated lymphoid tissue), the neonatal gut microbiota is responsible for the maturation of the immune system, and plays an important role in maintaining normal immune homeostasis and protecting against pathogens. Compared to adults, the infant microbiota is highly unstable and shows individual differences. It has fewer species and has a higher Bifidobacterium (digestive bacteria) ratio. The structure of the microbiota begins to change between the ages of 1 and 3 in early childhood, and from the age of 3 it becomes similar to the microbial communities seen in adults.

Depending on the mode of delivery, infants are exposed to maternal vaginal and intestinal microbiota at vaginal delivery (VD), while infants are predominantly exposed to maternal skin and environmental microbiota at cesarean delivery (CS). There is increasing evidence that abnormal gut microbiota develops as a result of mode of delivery and that this affects subsequent immune response regulation. Recent studies have reported an increased risk of asthma, obesity, celiac disease, and type 1 diabetes atopic eczema in children born with CS compared with VD. It has been explained that this increased risk is a result of the lack of contact with maternal vaginal and intestinal flora at birth with CS, and therefore the change in the microbial colonization pattern, and the susceptibility to certain diseases increases due to the changes in the development of the immune system of these children. Especially in the last two decades, birth rates with CS have increased rapidly around the world. At the same time, abnormal intestinal microbiota development has been detected in infants born with CS. In infants born with CS, the lack of contact with the mother's vaginal microbiota may be a possible reason for the greater colonization of microorganisms from the Firmicutes phylum (associated with obesity), and the lower colonization pattern of the Bacteroidetes phylum.

   In the first trimester vaginal microbiome diversity study by Haque et al., less diversity was observed in the vaginal microbiomes of women who had preterm labor during the first 15-20 weeks of pregnancy. However, it is not clear whether the gut microbiome changes during pregnancy. Study on preterm maternal gut microbiome shows an association between low bacterial diversity and risk of spontaneous preterm birth. All known potential maternal factors such as age, antibiotic use during pregnancy, ethnicity, body mass index, smoking at the beginning of pregnancy and education, and preterm birth were stronger. Nelson et al. In their study, a lower bacterial richness and diversity was found in the vaginal microbiota of women who gave preterm delivery compared to women who gave term birth. Low gut diversity and different microbial composition increase the possible risk of preterm delivery in women who tend to have increased inflammation during pregnancy.

   Mitsou et al. While they stated that the colonization rates of Bifidobacterium species in stool cultures taken on the 4th and 30th days of babies born with CS were significantly lower than those born with VD, Gonlund et al. could not confirm this relationship. Bezirtzoglou et al. reported similar colonization of the genus Bifidobacterium in CS and vaginally born babies. Inconsistency in studies of colonization pattern in relation to mode of delivery may be due to microbiota isolation and analysis techniques. The lower incidence of lactobacilli in the infants of mothers who gave birth by cesarean section suggests that the source of lactobacilli in the infant gut is mainly dependent on the maternal vaginal and – especially to a lesser extent – ​​anal microbiota during VD. In this context, the colonization of some important Lactobacillus species occurs in the babies of mothers who gave birth with CS in later periods. In addition, the lower abundance of Bifidobacteria and Bacteroides in babies born with CS, and the higher incidence of Haemophilus (influenzaB), Veillonella, Klebsilla and Clostridia can be explained by the use of antibiotics. In particular, postnatal antibiotic consumption is associated with an excess of Clostridium leptum and a decrease in the number of Bifidobacterium and Bacteroides. Prevalence of Clostridium species in those born with CS is associated with nosocomial (hospital-acquired) infections and severe gastrointestinal infections in infancy.

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