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. Author manuscript; available in PMC: 2021 Mar 1.
Published in final edited form as: Autism Res. 2019 Aug 29;13(1):134–144. doi: 10.1002/aur.2196

Figure 1.

Figure 1

Hazard ratios and 95% confidence intervals of maternal smoking in pregnancy and autism spectrum disorder with and without co-occurring intellectual disabilities (ID) and attention deficit hyperactivity disorder (ADHD), arising from three statistical designs: a conventional proportional hazards model stratified by year of birth, and adjusting for sex, parity, maternal and paternal age at birth, maternal and paternal psychiatric family history, maternal and paternal income, maternal and paternal education; a maternal cluster model including all covariates from the conventional model with the addition of adjustment for the family mean of maternal smoking in pregnancy; a discordant sibling model including all covariates from the conventional model with the addition of stratification by maternal sibling sets.