Autistic adults are often perceived as having an atypical speech. The acoustic characteristics of these impressions prove surprisingly difficult to delineate, but one feature that does robustly emerge across different studies is higher pitch (F0 values) in autistic versus neurotypical individuals. However, there is no clear explanation why autistic individuals should have higher-pitched voices. We propose that the solution lies in the gender imbalance still prevalent in autism, which entails an overrepresentation of male participants in research on speech in autism. We analyse speech samples from a gender-balanced group of 40 autistic and 40 neurotypical adults, controlling for potential stress levels through electrodermal activity recordings. We find that autistic males tend to have higher pitch than neurotypical males, but that autistic females tend to have lower pitch than neurotypical females. The interpretation we put forth for our finding -- that the autistic versus neurotypical group difference in pitch goes in opposite directions between males and females -- is that autistic individuals tend to be less influenced by neurotypical gender stereotypes.