The association between maternal diabetes and risk of autism spectrum disorder in offspring was not completely consistent. We performed an updated and systematic review and meta-analysis with relevant studies published until 6 August 2020. We included 17 publications, describing 15 studies, including 1,751,537 participants. Exposure to maternal diabetes in utero was correlated to an increased risk of ASD (effect estimate 1.30 [95% CI: 1.16-1.46]). Offspring exposure to maternal diabetes with antidiabetic medication has a heightened risk of ASD by 48% than offspring with a non-diabetic mother, and 42% than offspring with diabetic mother not receiving medical treatment. Exposure to maternal diabetes in utero increases the risk of ASD in offspring, especially exposure to maternal diabetes with antidiabetic medication.