The possible link between prenatal acetaminophen (Tylenol) use and childhood asthma is a topic that has been gaining the attention of researchers over the past decade.
This most recent study reviewed evidence from six studies on the topic.
When they combined the results of all studies, authors found that any prenatal exposure to acetaminophen was associated with a greater likelihood of children ages 2 ½ to 7 years old developing persistent wheezing.
However, the authors caution that more research is needed before a true conclusion can be drawn.
The studies used were slightly contradictory. One study showed no increased risk of asthma with Tylenol exposure, one study showed increased risk of wheezing only when other risk factors were present, and the four other studies did show an increased risk. One study showed the greatest risk of asthma occurred when mothers used Tylenol in the first trimester of pregnancy, while two studies showed greatest risk occurred in the second and third trimesters.
Two studies also showed an increased risk of allergies associated with prenatal Tylenol use.
One possible explanation for this association is that Tylenol can cause changes to the lining of the respiratory tract, allowing for increased inflammation. Inflammation is one of the main components of asthma.
Interestingly, one of the studies demonstrated a possible genetic cause for the increased risk of asthma. This study, published in 2010 by Columbia University, used a population of low income African American and Dominican children in New York City.
They showed that the highest risk of childhood asthma in relation to prenatal Tylenol exposure with associated with a specific gene. This gene could decrease the child's ability to properly break down the Tylenol, leading to buildup of chemicals that could increase lung inflammation.
One of the main problems with this recent study is that additional factors associated with the development of asthma, such as maternal smoking, viruses, pets, breastfeeding, and social class, were not accounted for.
This makes it difficult for the authors to confidently say that there is a direct cause and effect relationship between Tylenol and asthma. However, the results of this study were comparable to another large analysis study in 2009, which did take these factors into account.
Some children are more susceptible to development of asthma, possibly due to underlying genetic factors and both prenatal and neonatal exposures.
This study gives us an interesting possibility of another risk factor. There is not enough evidence to support any changes in the recommendation of Tylenol use in pregnancy. Tylenol remains the safest drug to treat pain and fever in pregnancy.
