An extensive Israeli study has found that mothers who continuously use a popular pain relief medication during their pregnancy face an increased risk of the newborn suffering from autism or ADHD.

The meta-analysis by a team of researchers from the Hebrew University of Jerusalem, published Tuesday in the American Journal of Epidemiology, showed that prolonged exposure to acetaminophen — also known as paracetamol — during pregnancy is associated with a 30 percent increase in relative risk for attention deficit hyperactivity disorder (ADHD) and a 20% increase in relative risk for autistic spectrum disorder (ASD), compared with those who did not take acetaminophen during pregnancy.

Acetaminophen is one of the most common medications used for treatment of pain and fever reduction and is considered relatively safe. It is marketed in Israel and around the world under many brands, including acamol and dexamol.

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Researchers, led by Dr. Ilan Matok, said it was the first meta-analysis and the “most comprehensive study ever conducted” on the possible association between prolonged use of acetaminophen during pregnancy and risk of autism or ADHD. The research data covered 132,738 mother and child pairs with a follow-up period of three to 11 years.

However, the academics urged caution given the significant limitations of existing studies, upon which the meta-analysis was based.

“The researchers believe the results should be interpreted with caution, as they may cause unnecessary anxiety among pregnant women,” the Hebrew University said in a press release Tuesday. “It is important to understand that pain and fever during pregnancy can have a detrimental effect on the developing fetus and that acetaminophen is still considered a safe drug for use during pregnancy.

“Therefore, if a pregnant woman has fever and/or pain, acetaminophen can be taken for a short period, and if the fever or pain continue beyond that, she should consult her physician regarding further treatment,” the statement continued.

Evidence of neuro-disruptive properties in acetaminophen has been accumulating. Past studies have shown that long-term administration of low doses of acetaminophen may affect the development of the fetal nervous system, and that this effect is often seen years after exposure, during childhood.

The systematic review and meta-analysis was conducted by Dr. Matok of the Institute for Drug Research in the School of Pharmacy at the Hebrew University’s Faculty of Medicine, together with doctoral student Reem Masarwa and Dr. Amichai Perlman and Dr. Hagai Levine of the Hebrew University and Hadassah Medical Center.

“The observed increase in risk was small, and the existing studies have significant limitations,” Matok said. “While unnecessary use of any medication should be avoided in pregnancy, we believe our findings should not alter current practice and women should not avoid use of short term acetaminophen when clinically needed.”