Possible preventive measures and proposed interventions that can help to reduce the risk of BCP-ALL development in genetically predisposed children. Before birth, maternal uptake of folic acid and a healthy diet (brown) have been associated with a reduced risk of BCP-ALL development. Maternal infection in pregnancy is associated with a significantly increased BCP-ALL risk related to viral transmission. After birth, trained immunity (green) and microbiome diversity (yellow) are important factors supported by epidemiological (filled bars) or experimental (striped bars) evidence. Immunity can be trained through vaccinations (TIBVs) before the age of 3 months, by breastfeeding and by social and livestock contacts (including pets) in the first year of life. Microbiome diversity is supported by a natural delivery and gradually builds up after birth. Again, breastfeeding and social and livestock contacts in the first year of life also have a beneficial impact on gut microbial diversity. Although only demonstrated in experimental models, the avoidance of overuse of antibiotics, the application of probiotics and a diet consisting of microbiome-supportive fibers are interventions that could also reduce the risk of leukemia development. Exposure of parents and children to various harmful chemicals can influence the microbiome along with carcinogenic effects.^164-166 Further evidence needs to be generated through large population-based studies to identify preventive measures and to substantiate initial data on vaginal seeding and fecal transplants.