Industrialisation has introduced several lifestyle changes and medical advancements but their impact on intestinal microbiota acquisition is often overlooked. Even though these consequential changes in the microbiota could contribute to the disease burden that accompanies industrialisation, such as obesity and atopic disease. A healthy intestinal microbiota is acquired early in life but its exact origin is not fully elucidated. The maternal microbiota is a likely source because the infant and mother intestinal microbiota share identical strains. Successfully transmitting microbes from mother to child requires microbes in the maternal donor, contact between the maternal source and the infant, and an acquiring infant recipient. Transmission can be altered by changes to any of those three transmission determinants: (1) maternal microbiota sources are shaped by the mother's genotype, diet, health status and perturbing antimicrobial exposure; (2) maternal contact is reduced through C-section and formula feeding and (3) engraftment in the infant recipient is determined by host habitat filtering, the established microbes and antibiotic disruptions. This review gives an overview of the possible maternal transmission routes, the disruptions thereof, and the missing links that should be addressed in future research to investigate the maternal transmissions that are crucial for obtaining a healthy infant microbiota.
Keywords: Infant intestinal microbiota; gastro-intestinal-tract health; human milk; missing microbes; vertical transmission.