Maternal tobacco smoking and offspring autism spectrum disorder or traits in ECHO cohorts.
Irva Hertz-Picciotto, Susan A Korrick, Christine Ladd-Acosta and 24 others
PMID 35199959WHAT IT FOUND
Maternal smoking showed no link to autism diagnosis in the main analysis.
However, when excluding biased study designs, a 1.44-fold increased odds of diagnosis emerged. Smoking was consistently linked to higher scores for social impairment traits.
Key findings
01The primary pooled analysis of 11 cohorts found no association between maternal smoking and autism diagnosis, with an odds ratio of 1.08.
02After excluding cohorts with small case numbers or preterm birth designs, the odds of an autism diagnosis among children of smoking mothers rose to 1.44.
03Children of mothers who smoked scored 2.37 points higher on the Social Responsiveness Scale, indicating greater social impairment.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Smoking status was self-reported by mothers, and biomarkers suggest about 25% of pregnant smokers do not disclose their habit, which biases results toward showing no effect. Exposure was treated as a simple yes/no variable, ignoring the timing, amount, or second-hand smoke exposure. Several cohorts relied on parental report or medical records for autism diagnosis rather than gold-standard instruments, which can inflate prevalence estimates. The analysis did not account for paternal smoking, which is highly correlated with maternal smoking and may independently influence child outcomes.
Declared interests
The authors declared no conflicts of interest. The study was funded by the National Institutes of Health.
The easy way to misread this
Do not conclude that maternal smoking causes autism based on the main analysis, which was null. The positive finding of a 1.44-fold increased odds emerged only after excluding specific cohorts, and the study design cannot prove causation or rule out residual confounding.