Gender Differences During Toddlerhood in Autism Spectrum Disorder: A Prospective Community-Based Longitudinal Follow-Up Study.

Fleury et al. (2018) followed toddlers with autism in everyday clinics. They tracked boys and girls to see if autism looks the same at age two.

No extra tests were given. The team simply watched who got flagged and how severe the signs were.

Overall severity was the same for both sexes. Yet girls showed quieter social-communication gaps, like less eye contact or shared pointing.

Because the gaps were subtle, the girls’ autism risk was easier to overlook during routine check-ups.

Matson et al. (2009) and Ros-Demarize et al. (2020) saw the same pattern: toddler girls had weaker social communication while boys showed more hand-flapping or lining up toys. These studies strengthen the signal that girls can be missed.

Matheis et al. (2019) seems to disagree. After matching boys and girls for IQ, girls actually scored better on communication. The clash disappears when you see that Fleury et al. (2018) did not match for IQ; they captured the raw community sample where brighter girls still looked “less autistic” globally even though their social eye contact was weak.

Kocher et al. (2015) and Andersson et al. (2013) found zero sex differences in matched pairs. Their tight matching for age and development may have washed out the same mild social gap that Fleury et al. (2018) caught in the real-world mix.

For BCBAs doing early screenings, don’t let average or above-average cognitive scores relax your probe of social milestones in toddler girls. Ask about joint attention, showing, and social smiling even when the child talks in sentences. If the score is borderline, schedule a second look rather than a “wait and see.” Catching girls a few months earlier can shorten the later intervention gap.