The stress which many babies endure in the birthing process has been shown to be the cause of at least a portion of autism cases. A new treatment has been tested, showing that if the mother(in this case using rats) is given a diuretic, the newborns have a significantly decreased chance of autistic symptoms.
According to a February 6, 2014 interview, there are many supposed causes of autism, but they are not all defined. Influenza during pregnancy may also be a part of the autism statistic, but there are many other possible causes. The rates of autism are increasing each year, but no research group has been able to say exactly why. That is why these experiments have been called for.
What is known is that chloride plays a role and diuretics can assist in reducing its impact. In testing, these diuretics may lead to large decreases in chances for autistic offspring, but its use in humans is not yet safe. While the testing will still continue, there is no known time when this type of effort may lead to human treatment.
For a broad summary of the research: http://www.nbcnews.com/health/kids-health/autism-study-points-way-calmin...