Babies with the most acetaminophen in cord blood had more autism later
Acetaminophen turned up in all 996 stored cord-blood samples. Against the lowest third, the highest had odds of 3.62 for autism and 2.86 for attention-deficit disorder by about age ten.
What the study found
The highest third by cord-blood exposure had triple the autism odds
Rather than asking mothers what they remembered taking, this study assayed acetaminophen in stored cord plasma from 996 births and found it in every sample. Against the lowest third, the highest had odds of 3.62 for autism and 2.86 for attention-deficit disorder by about age ten.
The caveat · No comparison between siblings
There is no sibling or family-based control here, which is the design that dissolved associations of exactly this shape. Cord blood at delivery captures the hours and days before birth, so a gradient in late exposure is standing in for exposure across a whole pregnancy. Fever, infection and pain are themselves linked to these outcomes and are the reason the drug gets taken, which stratifying by recorded indication does not fix. This cohort is low-income, urban and enriched for preterm birth, and 26% of it had an attention-deficit diagnosis against a few percent in the general population.
What we don't know
Measuring paracetamol in cord blood is a better way to know who was exposed, and here it found a link. What it cannot do is separate the drug from what leads a family to take it; sibling studies can, and find none. The question stays open.