Comparing brothers and sisters, the autism link did not hold
In 2.48 million Swedish children, hazard ratios of 1.05 to 1.07 for autism, attention-deficit disorder and intellectual disability fell to about 1 once siblings were compared.
What the study found
Compare siblings and the pregnancy signal disappears
In 2.48 million Swedish children, hazard ratios of 1.05 to 1.07 for autism, attention-deficit disorder and intellectual disability fell to about 1 between siblings, as in Hong Kong. There, the usual design also linked use before pregnancy, which cannot cause anything: it is confounded.
The caveat · Shop-bought use largely unrecorded
Sibling comparison removes what families share but keeps only the families whose pregnancies differed, which is an unusual subset by construction, and it magnifies any error in recording who was exposed. Exposure came from antenatal notes and dispensing records in countries where paracetamol is sold freely, so a large share of real use is invisible: the Hong Kong figure of 43% exposed sits well below what surveys find. A null across these three diagnoses is not a clean bill of health for outcomes nobody measured. One author of each study declares payments from law firms or consulting in an area under active litigation.
What we don't know
Whether paracetamol in pregnancy raises autism or attention-deficit risk is still open. Comparing siblings best separates the drug from the family and finds no link; measuring it in cord blood best shows who was exposed and finds one.