**2. Literature review**

#### **2.1 Overview of the neonatal microbiome and its importance in health**

The neonatal microbiome refers to the collection of microorganisms, including bacteria, viruses, fungi, and other microbes, that inhabit the newborn's body, particularly the gut, skin, and mucous membranes. The newborn microbiome experiences rapid development and is essential for many aspects of development and health. During pregnancy, the fetus is believed to be in a relatively sterile environment. However, upon birth, the neonate is rapidly colonized by microorganisms from the surrounding environment, primarily influenced by the mode of delivery, feeding practices, maternal factors, and exposure to the external environment. The early establishment of a diverse and balanced neonatal microbiome is important for multiple physiological processes [7–9].

Immune system development: The neonatal microbiome plays a crucial role in the maturation and development of the immune system. The presence of beneficial bacteria in the gut stimulates the production of specific immune cells and regulatory molecules, promoting immune tolerance and preventing exaggerated immune responses. The interaction between the microbiome and the immune system is essential for the proper functioning of immune defense mechanisms and protection against infections [7–9].

Metabolic processes: The neonatal microbiome is involved in various metabolic processes, including the fermentation of dietary components and the production of essential metabolites. Beneficial bacteria in the gut can break down complex carbohydrates that are indigestible by the host, producing short-chain fatty acids and other metabolites that provide energy to the host cells and contribute to overall metabolic homeostasis [9–11].

Protection against pathogens: A defense against possible infections is provided by the newborn microbiota. Pathogens are kept from colonizing and overgrowing by beneficial bacteria in the gut and on the skin, which compete with them for nutrition and space. Additionally, they create antimicrobial chemicals that can obstruct the development of viruses and bacteria that cause disease [9–11].

Maturation of organ systems: The neonatal microbiome has been implicated in the maturation and development of various organ systems. It influences the development and integrity of the intestinal epithelial barrier, aiding in nutrient absorption and preventing the translocation of harmful substances into the

*Vaginal Seeding in Term Cesarean Section Is a Mandatory Condition for Improvement… DOI: http://dx.doi.org/10.5772/intechopen.114043*

bloodstream. Additionally, the microbiome can influence the development of the central nervous system and the modulation of neurotransmitters, potentially affecting neurodevelopmental processes.

Association with health and disease: Alterations in the neonatal microbiome have been associated with various health conditions and disease outcomes. Dysbiosis, an imbalance or disruption in the microbial composition, has been linked to an increased risk of allergies, asthma, obesity, autoimmune disorders, gastrointestinal disorders (such as necrotizing enterocolitis), and even neurodevelopmental disorders. Understanding the role of the neonatal microbiome in these health conditions can help develop targeted interventions and strategies for prevention and treatment [9–11].

The neonatal microbiome is a dynamic ecosystem that influences various aspects of health and development. Its establishment and composition in the early stages of life play a crucial role in immune system maturation, metabolic processes, pathogen defense, and the development of organ systems. Understanding the importance of the neonatal microbiome provides insights into the potential impact of interventions, such as vaginal seeding on health outcomes and underscores the need for further research to optimize neonatal health [9–11].
