There is growing evidence suggesting that the environment contributes to the etiology of autism spectrum disorder (ASD). Environmental factors aren’t genetically determined, which can make them reversible or avoidable in some cases. Anyone can be exposed to them without necessarily being able to control the exposure and be affected by them but in heterogeneous ways. Furthermore, their effects can be long lasting. We have searched through literature regarding ASD and environmental factors, which ones are linked to ASD and why. We found information on parental age, maternal psychosocial stress, maternal chronic diseases, infection during pregnancy, obstetrical complications, and postnatal toxic exposure, among others. How and why, they affect some individuals isn’t always clear. Timing of exposure has proven to play a part in how it could affect fetus and children. The following mechanisms have been postulated to bridge environment and ASD: inflammation, oxidative stress, mitochondria, and microbiota as well as epigenetics. These risk factors have been involved in neuropsychiatric conditions other than ASD, but some could be specific to ASD. Because of these possible specific factors, we have added some items to a preexisting questionnaire: “Histoire du développement” and hope to carry on with the research on environmental factors. The questionnaire is a self-report questionnaire for parents that incorporates questions regarding early development. It remains to be seen which environmental factors are part of the pathogenesis of ASD and which ones accompany an unfavorable in utero and postnatal environment without directly causing harm on the fetus’ brain.