The mothers of 54 non-autistic boys were surveyed, and 7.4% of them had at least one diet soda per day.
The mothers of 67 non-autistic girls were surveyed, and 17.9% of them had at least one diet soda per day.
The mothers of 140 autistic boys were surveyed, and 19.3% of them had at least one diet soda per day.
The mothers of 28 autistic girls were surveyed, and 10.7% of them had at least one diet soda per day.
They did some analysis that was supposed to control for income, education, ethnicity, and geographical location to get the odds ratios and confidence intervals that other people are commenting.