All manner of things may effect fertility. There are different medications, diets, additives, lifestyles, pollutants, household products than 25 years ago. Some of the higher incidence may be a change in diagnoses.
If something was causing a greater number of mutations, we would be seeing an increase in all kinds of birth defects and cancers.
That doesn't necessarily follow.
Interesting that you mention fertility. What else is different in the past 25 years is the treatment of infertility. I’m sure someone has done the studies trying to correlate: maternal age, paternal age, fertility treatments used/not used with the incidence of autism.