March 30, 2011 -- Pregnant women who take the popular painkiller acetaminophen (Acephen, Actamin, Feverall, Tylenol, and Uniserts) may be boosting their baby's risk of asthma, according to a new report.
But the findings should not be cause for alarm, says study researcher Richard Beasley, MD, professor of medicine at the Medical Research Institute of New Zealand. "It is still considered a safe drug to take and our findings don't alter that recommendation.”
What is not known, he tells WebMD, is whether the link between the use of painkillers during pregnancy and asthma in the child is truly cause and effect.
"The message would be that this study raises some concern, and that it really reinforces the general principle to avoid unnecessary medication during pregnancy," he says. "This [report] does not change the recommendation."
Acetaminophen, called paracetamol in New Zealand, would ''remain as the preferred analgesic'' to bring down fever in a pregnant woman, he says. "But we would caution against the regular use, particularly regular unnecessary use, during pregnancy.”
The report is published in the journal Clinical & Experimental Allergy.
Painkillers During Pregnancy
Previous research, including some by the New Zealand researchers, has suggested that use of the painkiller during pregnancy may increase asthma risk in children.
In the new report, Beasley and his colleagues re-evaluated the results of six previously published studies.
Overall, Beasley found that the use of the painkiller by pregnant women during any stage of pregnancy was linked with a 21% increased risk of asthma in their young children.
The increasing use of acetaminophen, some experts say, may have contributed to the rising rates of asthma worldwide. In the U.S., 24.6 million people, about 8.2% of the population, have asthma, according to the CDC.
In the six studies, the children ranged in age from 2 1/2 to 7. Parents were asked if their child had wheezing in the last 12 months.
"'We would say wheezing is a marker for asthma," Beasley tells WebMD.
No information was available on the dose of painkiller taken or how often.
The results from the separate studies vary. One Spanish study, for instance, found a link between the use of acetaminophen by the mother at least once a month during pregnancy and the chance her child had wheezing by preschool age. But the link was only found among mothers without asthma, not those who had asthma.
In a U.S. study of 1,505 women, the use of acetaminophen did not increase the risk of asthma overall. And in mothers who used it only during the first or third trimesters, it was linked with a reduced risk of asthma.
Researchers cannot explain the link, when found, Beasley says. One speculation is that the breakdown products of the painkiller may increase the risk of inflammation. If the inflammation affects the airway, he says, that could increase the risk of asthma.
The new report ''does strengthen the argument" linking painkiller use during pregnancy with asthma, says Victoria Persky, MD, professor of epidemiology and biostatistics at the University of Illinois at Chicago School of Public Health.
In her own research, published in 2008, she found infants born to women who used acetaminophen in mid to late pregnancy had an increased risk of wheezing in the first year of life. She found no link if the medicine was used early in pregnancy.
However, she says, more data are needed. "I think it's still premature for a public health recommendation."
Another expert, Rebecca Piltch, MD, a San Francisco allergist, agrees that the evidence is preliminary. However, she says, "It is beginning to look like there may be a link at least in some circumstances."
Charles Lockwood, MD, chair of obstetrics, gynecology, and reproductive sciences at Yale University, says the studies have some built-in bias. "Mothers with asthma and frequent upper respiratory infections use more paracetamol and are already at risk for having affected children.”
The American Congress of Obstetricians and Gynecologists does not offer guidance on the use of acetaminophen during pregnancy, says Stacy Brooks, a spokesperson.
''On balance, it is still the safest pain medication," Lockwood says.
Bonnie Jacobs, a spokeswoman for the maker of Tylenol, Johnson & Johnson's McNeil Healthcare, says her experts have not yet evaluated the study.
She withheld comment until the experts had a chance to evaluate the new results thoroughly.