Prenatal mercury exposure and features of autism: a prospective population study.
Jean Golding, Dheeraj Rai, Steven Gregory and 5 others
PMID 29713443WHAT IT FOUND
Prenatal mercury exposure was not associated with autism diagnosis or autistic traits in children.
A possible adverse link appeared only among mothers who ate no fish.
Key findings
01Prenatal total blood mercury was not associated with diagnosed autism after adjustment for key confounders.
02Prenatal mercury levels were not associated with the autistic trait measures.
03Among children of mothers who did not eat fish, higher prenatal mercury was associated with poor social cognition, unlike children of mothers who ate fish.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only 45 of the 177 children with a presumed autism diagnosis had prenatal blood mercury measured, so the analysis of diagnosed autism had limited power. Autism cases were identified from records, questionnaires and parent reports, not a specific examination, so some cases may be misclassified. Mercury was measured only in early pregnancy, and exposure later in pregnancy could matter. Fish consumption was not characterized by fish type, so mothers who ate high-mercury predatory fish could not be identified. The blood samples were stored for 18 to 19.5 years before analysis. Some mercury could have leaked, and this could bias results toward null. The mercury levels in this UK population may differ from other populations. The significant findings were secondary subgroup or proxy analyses, and the authors say the social cognition result needs testing in other populations.
Declared interests
No author conflicts of interest declaration is included in the supplied text. The publication types list NIH intramural and other government research support.
The easy way to misread this
Do not conclude that prenatal mercury protects against autism or that it causes autism. This was an observational population study, not a trial of mercury exposure. The main adjusted analysis for diagnosed autism was null. The significant subgroup result involved children of mothers who ate no fish, and the authors say it needs testing in other populations.