Both genetic and environmental factors play a role in the development of vision disorders. Family history is a risk factor for some vision disorders such asrefractive error, as is premature birth. The presence of some vision disorders increases the likelihood of developing other vision disorders, such as strabismus and amblyopia. A number of neurodevelopmental disorders (e.g., cerebral palsy, Down syndrome, autism spectrum disorders, hearing impairment and speech delay) also are associated with higher rates of vision problems. The most significant preventable risk factor for visual disorders in children is maternal smoking. Children of women who smoked cigarettes during pregnancy have higher rates of strabismus, hyperopia, and astigmatism.