Perinatal and maternal risk factors for autism spectrum disorders in New South Wales, Australia


  • Changes in author affiliations: Author Katrina Williams is now at Sydney Children's Hospital and University of NSW; Author Megan Helmer is now at Eli Lilly Australia; Author Glen W Duncan is now at Charles Sturt University; Author Jennifer K Peat is now working as a consultant statistician; Author Craig M Mellis is now working only for University of Sydney.

Katrina Williams, Sydney Children's Community Health Centre, Cnr Barker and Avoca Streets, Randwick NSW 2031, Australia


Background  This study was commenced in 1999 with the aim of examining risk factors for autism using established population-based data for comparison.

Methods  Cases were ascertained using active surveillance and compared with birth data.

Results  Four risk factors were found to be significantly associated with autism using binary logistic regression analysis; being male [adjusted odds ratio (OR) 4.7, 95% confidence interval (CI) 3.2–7.0], being born prematurely (adjusted OR 2.2, 95% CI 1.5–3.5), having maternal age ≥35 years (adjusted OR 1.7, 95% CI 1.2–2.4) and having a mother born outside Australia (adjusted OR 1.4, 95% CI 1.0–1.9). For analysis completed for pregnancies, rather than live births, multiple birth was also a significant risk factor for one or more children of the pregnancy to be affected by autism (adjusted OR 2.5, 95% CI 1.1–5.5). There was a statistically significant trend towards increasing risk with increasing risk factor ‘dose’ for gestational age (P = 0.019), multiple birth (P = 0.016) and maternal age (P < 0.001). For mother's country of birth the group with the highest risk were children of mother's born in south-east or north-east Asia. There was a non-significant trend towards a higher proportion of children with developmental disability having risk factors.

Conclusion  Replication of risk factors from previous studies and a significant risk factor ‘dose’ effect add to growing evidence that maternal and perinatal factors are low magnitude risk factors for autism. The association between developmental disability and autism risk factors warrants further examination.