A new study has revealed novel environmental risk factors for paediatric-onset multiple sclerosis (MS) that seem to act in the perinatal period. The team studied 265 individuals with paediatric MS and 412 healthy controls, and found that illness of the mother during pregnancy was associated with a 2.3-fold increase in the risk of MS in the offspring. By contrast, caesarean delivery was associated with a 60% reduction in MS risk. The researchers also found an association between paediatric-onset MS and pesticide exposure: the offspring of fathers with a gardening-related occupation had a 2.8-fold increase in MS risk, and use of pesticide products in the household yielded a 1.7-fold increase in the risk of MS. The investigators note that more research is required to characterize the part played by these factors in MS pathogenesis.