Comparison of Perinatal Risk Factors Associated with Autism Spectrum Disorder (ASD), Intellectual Disability (ID), and Co-occurring ASD and ID.

The team pulled birth records for three groups: kids with autism only, kids with intellectual disability only, and kids with both.

They counted how often each group had preterm birth, low birth weight, low Apgar scores, and small-for-gestational-age.

Then they stacked those rates against the general U.S. population to see who stood out.

All three groups had more early birth trouble than the national norm.

The ID-only group showed the clearest jump; the autism-only and combined groups looked about the same as each other.

In short, early medical red flags are linked to later developmental diagnoses, but the link is strongest when ID is in the picture.

Atladóttir et al. (2015) ran a direct replication the same year and saw the same pattern: neonatal problems pile up for ASD, ID, and combined kids alike.

Two older papers seem to disagree. Howard et al. (1988) found no extra birth problems once IQ was matched across groups, and Dall et al. (1997) saw no gap between autistic children and their own siblings.

The gap closes when you control for IQ or use brothers and sisters as controls, so the extra risk is tied more to intellectual disability than to autism itself.

Perales-Marín et al. (2021) extend the idea by showing each ASD subgroup now carries its own prenatal risk signature, moving the story from birth backward into pregnancy.

When you read an intake file full of preterm or low-Apgar notes, expect a higher chance of global delays, not just autism traits.

Plan deeper cognitive screens and adjust your skill sequencing; kids with ID often need smaller steps and more chaining.

Share the medical history with the pediatrician—early birth data can help the whole team set realistic timelines and flag possible seizure or motor issues down the road.