Planting the seed: Origins, composition, and postnatal health significance of the fetal gastrointestinal microbiota

Abstract

It has long been assumed that establishment of the fetal microbiome commences with the birthing process. However, recent studies have found bacterial DNA in umbilical cord blood, placenta, amniotic fluid, meconium, and fetal membranes in healthy normal pregnancies, leading to suggestions that the seeding of the fetal microbiome may commence in utero long before delivery. The origins of the microbiota of the fetal gastrointestinal (GI) tract have not yet been conclusively determined, although bacterial translocation from the maternal circulation, or ascension from the vagina, are both likely to be contributing pathways. Mother-to-child efflux of bacteria during pregnancy has the potential to markedly influence postnatal health, as the composition of gut microbiota determines production of important metabolites which are absorbed systemically and which modify immune function and development. Hence, the importance of understanding the colonization of the fetal GI microbiome is becoming clear, although few studies have investigated the origins, dynamics, and timing of the fetal microbiome. This is the topic of this review. By gaining a deeper understanding of the mechanisms underpinning fetal microbiome seeding, strategies may be developed to optimize fetal immune development and reduce the risk of adverse health and developmental outcomes.

Specific class of intrapartum antibiotics relates to maturation of the infant gut microbiota: a prospective cohort study

“…6 Acquisition of the microbiome in infancy is required for competent immune maturation. [7][8][9] In healthy neonatal populations, colonisation may begin during fetal life, [10][11][12] with a substantial introduction of microbes during the process of delivery, [13][14][15][16] and in early infancy. [17][18][19][20] Emerging data indicate that exposure to antibiotics during early infancy leads to persistent alterations in immune functions that are primarily implicated in the cause of allergic and atopic disease.…”

Feeding modes shape the acquisition and structure of the initial gut microbiota in newborn lambs

“…Mounting evidence suggests that the early development of the gut microbiota of newborns is essential for health by maintaining intestinal homeostasis and barrier function, stimulating development of the immune system, contributing to nutrient digestion, and protecting against pathogens (Sekirov et al, 2010;Maynard et al, 2012;Wopereis et al, 2014). The symbiotic microbe-host interactions during the earliest days of life critically determine life-long health (Rautava et al, 2012;Stinson et al, 2017;Korpela and de Vos, 2018). Disruption of the early gut microbiota has been linked to diseases in later life, including obesity, metabolic diseases, inflammatory bowel disease, irritable bowel syndrome, necrotizing enterocolitis, and autoimmune diseases and allergy (Rautava et al, 2012;Christian et al, 2017).…”

Respiratory microbiota and lower respiratory tract disease

“…There is recent evidence of foetal microbial colonization starting in utero, 12,13 with intensification of the process immediately after birth. Maternal bacteria rapidly colonize cutaneous and mucosal surfaces of the newborn, with predominance of vaginal and intestinal maternal microbiota in case of vaginal delivery, and of skin microbiota in births resulting from caesarean sections.…”