There has been a been dramatic increase starting in the early 1980’s of an increase in pediatric asthma. During that time there also has been an increased usage of acetaminophen and ibuprofen to treat fever related illnesses in children. There have many many studies that have reported a correlation with increased use of these medications and asthma risk. Although many of these studies are limited by children getting respiratory tract infections, which in itself is a risk factor for asthma.
A recent study was done, which took into account and adjusted for respiratory tract infections early in life. It showed a substantially diminished association between usage of these medications and early childhood asthma, demonstrating that perhaps it has more to do with the upper respiratory infections, i.e. RSV.
Although prenatal Tylenol exposure was associated with an increased risk of wheeze and asthma in early childhood but not mid childhood, but the study did not explain why the mothers were taking Tylenol, which could also have been playing a role in why there was increased asthma risk.
There needs to be a lot more studies that need to be done to answer the question, does tylenol cause asthma? It is very difficult to do studies in pregnant woman though. There are very limited options of medications for pregnant woman and the choice of alternative medications is very limited.
The take home message would be to have a higher threshold of any medication during pregnancy. Avoidance of excessive, unnecessary or inappropriate usage is highly advised. Any medication can have a potential side effects even if they are over the counter. If there is any question of whether a medication is safe to use during pregnancy, one should consult there OB/GYN. Although in this study, it shows respiratory infections during pregnancy shows a strong correlation to increased asthma risk.