Prenatal Acetaminophen: An Asthma Link?

Pregnant Women Who Take Acetaminophen Could Raise Asthma Risk in Their Kids

Reviewed by Louise Chang, MD on March 19, 2008
From the WebMD Archives

March 19, 2008 (Philadelphia) -- Some kids whose moms take acetaminophen during pregnancy may be more likely to have asthma symptoms, a new study suggests. Acetaminophen is the active ingredient in painkillers such as Tylenol.

Researchers found that 5-year-old children of high-risk mothers who took acetaminophen in pregnancy were 70% more likely to suffer wheezing than kids whose moms didn't take the medicine-cabinet staple.

Taking acetaminophen in the was most risky, increasing the odds that kids would have asthma symptoms by 90%.

But kids who took acetaminophen when they were age 1, 2, or 3 were no more likely to have breathing difficulties at age 5 than their counterparts who didn't take the drug.

The findings were presented here at the annual meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI).

High-Risk Families Studied

The researchers studied only families at high risk of developing asthma "not because of individual risk factors like family history but because they were living in inner-city neighborhoods where asthma is common," says Matthew S. Perzanowski, PhD, assistant professor of environmental health sciences at Columbia University's Mailman School of Public Health in New York City.

"But it's possible the findings are generalizable" to other families as well, he tells WebMD. Five-year-olds whose moms took acetaminophen in pregnancy were also more likely to have trouble sleeping, to have been rushed to the emergency department, and to have used other medications, "all things associated with wheezing in asthmatics," Perzanowski adds.

Wheeze Risk Rises as Acetaminophen Use Goes Up

The study does not prove cause-and-effect. And the findings "may apply only to the inner-city population in which it was carried out," says Andy Nish, MD, of the Allergy and Asthma Care Center in Gainesville, Ga.

"While acetaminophen is generally presumed to be safe, the study findings, while preliminary, are cautionary," Nish says.

But it did suggest that the more acetaminophen a woman took during pregnancy, the greater the risk her young child would suffer wheezing. That strengthens the possibility of a real link, Nish says. He was not involved with the work.

"Acetaminophen should not be taken without reason, particularly in women and children with a history or family history of allergic disease," he tells WebMD.

Asthma Rates Skyrocketing Among Kids

The asthma statistics for kids are frightening, Perzanowski says. Nine million U.S. children under 18 have been diagnosed with asthma. Asthma rates in children under 5 shot up more than 160% from 1980 to 1994, according to AAAAI.

Among children in the inner city, the picture is even bleaker. One study found nearly one in three youngsters under age 12 is affected.

While some experts have blamed increased exposure to allergens from cockroaches and mice and to air pollution for the unprecedented rise in asthma rates among these kids, Perzanowski says the timeline doesn't really fit.

Seeking another explanation, his team set out to determine whether taking acetaminophen during pregnancy or young childhood raises the risk of wheezing at age 5.

Study Details

The analysis, part of an ongoing study looking at the effect of pollutants ranging from secondhand smoke to pesticides on children's health, involved 712 nonsmoking mothers of African-American and Dominican ethnicity. All lived in low-income neighborhoods in New York City.

Once a year, the women were asked detailed questions about whether they or their children had symptoms of asthma and allergy. They were asked about their and their children's use of prescription and over-the-counter medications. With regards to the current analysis, Perzanowski says, "the specific question that women were asked was, 'Did you take Tylenol in pregnancy, and if so, for how many days?'"Additionally, their blood was tested for chemicals that have been implicated in the allergic cascade.

Overall, 34% of the moms took acetaminophen in pregnancy.

Wheezing rates among 5-years-olds were:

  • About 22% if their moms didn't take acetaminophen in pregnancy.
  • About 30% if they took it for one day.
  • More than 35% if they took it for two to four days
  • More than 50% if they took acetaminophen for five or more days

Compared with 5-year-olds of moms who didn't take acetaminophen in pregnancy, those whose moms took it for five or more days were 2.2 times more likely to have wheezing at age 5. If a mom took acetaminophen for two to four days, the risk went up 78%. Taking it for one day did not significantly raise the risk.

Perzanowski says that the women were also asked how much Tylenol they took, but the data are not yet fully analyzed. "But it looks like they support the current findings -- that is, the more Tylenol they took, the greater the risk their child had wheezing at age 5," he says.

The analysis took into account other risk factors for asthma including ethnicity, whether the mom had asthma, and whether she smoked during pregnancy.

So what could be happening? While no one knows for sure, Perzanowski says that acetaminophen use may deplete the lung of an antioxidant called glutathione. Researchers think glutathione, which is found in the lining of airways, may play an important role in preventing damage to the lungs.

Show Sources


American Academy of Allergy, Asthma & Immunology Annual Meeting 2008, Philadelphia, March 14-18, 2008.

Matthew S. Perzanowski, PhD, assistant professor, department of environmental health sciences, Mailman School of Public Health, Columbia University, New York City.

Andy Nish, MD, Allergy and Asthma Care Center, Gainesville, Ga.

AAAAI web site: "Asthma Statistics."

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