Figure 1.

Early exposure to amniotic fluid, nutrients and the microbiota influences gut-brain circuit development. Prior to birth, fetal swallowing exposes its gut to amniotic fluid, containing both nutrients and a developing microbiome. There, nutrients, microbiota and their metabolites come in contact with developing gut sensor cells—enteroendocrine cells—which form synapses with vagal nodose neurons. Dysregulation of the development of this gut-brain neural circuitry can have profound, prolonged effects on later health. Created with BioRender.