La Pediatria Medica e Chirurgica 2017; volume 39:184 Abstract The development of a proper neonatal microbiota is of great importance, especially for the effects that dysbiosis has in acute and chronic diseases’ onset. The microbiota, particularly the intestinal one, plays a crucial role in maintaining the health of the host, preventing colonization by pathogenic bacteria and significantly influencing the development and maturation of a normal gastrointestinal mucosal immunity. Several factors may interfere with the physiological develop- ment of microbiota, such as diseases during pregnancy, type of delivery, maternal nutrition, type of neonatal feeding, use of antibiotics, exposition to hospital environment (e.g., neonatal intensive care unit) and genetic factors. Thanks to a proper maternal and neonatal supplementation with specific functional nutrients, it is now possible to correct dys- biosis, thus reducing the risks for the newborn’s health. In this review of the literature, we give an overview of the studies highlighting the composition of the maternal, fetal and neonatal microbiota, the factors potentially responsible for dys- biosis and the use of functional nutrients to prevent diseases’ onset. Introduction In recent decades, several studies have shown that the increas- ing incidence of autoimmune, infectious and allergic diseases in pediatric and adult population may be closely related to dysbiosis, which is the alteration of the physiological development of human gut microbiota. For this reason, the study of microbiota and microbiome has become a priority to clarify the pathogenesis of these diseases, but also to plan a possible therapeutic and preventive intervention. The microbiota includes all the microorganisms that live in the human body. The human gut, especially the large intestine, has the greatest number of bacteria compared to any other part of the body. It contains about 10 14 microorganisms, which is ten times the number of human cells. After initial colonization, the intestinal microbiota composi- tion is unique for each individual, although more than 95% of the bacteria belong to four major phyla: Firmicutes, Bacteroidetes, Actinobacteria and Protecteobacteria. The development of this complex microbiota begins at birth and continues over the years. It plays a key role, influencing both intestinal and immune functions, as well as defending the organ- ism from external pathogens. For this reason, any interference with its development can be at the origin of several diseases. Before going into details of this review, we think it would be useful to provide a small glossary of the most common terms in the field of functional nutrients. Microbiota is defined as the sum of symbiotic microorgan- isms, which coexist within the human body without damaging it. On the other hand, the microbiome is the sum of genetic and envi- ronmental interactions of all microorganisms in a defined environ- ment, such as the human organism. Probiotics, according to the universally accepted definition of FAO/WHO, are living organisms that, when administered in an adequate amount, confer a benefit for the host’s health. Prebiotic is any substance present in food that is not absorbed in the gut but which selectively stimulates the growth and/or activity of one or a small number of bacteria in the colon. The majority of them are carbohydrates, especially oligosaccharides like fructooligosaccha- rides (FOS). The term symbiotic is used to indicate products that contain both probiotics and prebiotics; in this case, the combination of the two products is fundamental because each probiotic takes benefits from a specific type of prebiotics. 1 Recently, a new concept has been introduced: the fermented matrix. This product is obtained following the fermentation process carried out by beneficial bacteria of our organism (probi- otics), thus generating metabolites, called postbiotics, capable of performing anti-inflammatory, anti-microbial and anti-oxidant activity. Correspondence: Gianluca Lista, UOC Neonatologia, Patologia Neonatale e Terapia Intensiva Neonatale, Ospedale dei Bambini V. Buzzi, ASST FBF - Sacco - Buzzi, via Castelvetro 32, 20154 Milano, Italy. Tel.: +39.02.57995346. E-mail: gianluca.lista@asst-fbf-sacco.it Key words: Functional nutrients; probiotics; prebiotics; microbiota; fer- mented matrix. Contributions: the authors contributed equally. Conflict of interests: the authors declare no potential conflict of interests. Funding: Funded by Merqurio Editore S.r.l., with the unconditional contribution of Nestlè Italiana S.p.A. Received for publication: 6 November 2017. Accepted for publication: 19 December 2017. This work is licensed under a Creative Commons Attribution NonCommercial 4.0 License (CC BY-NC 4.0). ©Copyright G. Lista et al., 2017 Licensee PAGEPress, Italy La Pediatria Medica e Chirurgica 2017; 39:184 doi:10.4081/pmc.2017.184 [page 124] [La Pediatria Medica e Chirurgica - Medical and Surgical Pediatrics 2017; 39:184] Functional nutrients in infants born by vaginal delivery or Cesarean section Gianluca Lista, Fabio Meneghin, Ilia Bresesti, Francesca Castoldi UOC Neonatologia, Patologia Neonatale e Terapia Intensiva Neonatale, Ospedale dei Bambini V. Buzzi, ASST FBF - Sacco - Buzzi, Milano, Italy Non-commercial use only