A large study published in the International Journal of Epidemiology has found that taking acetaminophen, the pain reliever better known as Tylenol in the US and paracetamol in Europe, during pregnancy and in early infancy is associated with a slight increase in the risk for asthma in children.
The study is important but the increased risk involved is small. Studies like this bring home the idea that there is too little research being done on the effects of medications —both prescription and over-the-counter— taken during pregnancy and breastfeeding.
The study was conducted at the Norwegian Institute of Public Health and used health data from the Norwegian Mother and Child Cohort Study. It included more than 95,000 women who were pregnant between 1999 and 2008 and the 114,500 children to whom they gave birth. The study used questionnaires to ask mothers what medications they used for themselves and for their children up to age 6 months. The researchers then followed more than 53,000 of the children and also used data from the Medical Birth Registry of Norway and the Norwegian Prescription Database.
When they evaluated all this information, the researchers found that prenatal exposure to acetaminophen was linked with a 13% higher risk of asthma at age 3. The more acetaminophen the mother said she had taken during her pregnancy, the higher the risk of asthma for her child. And children who were given acetaminophen up to age 6 months were found to have a 29% higher risk of asthma at age 3.
The study was designed to minimize the possibility that the increased risk of asthma was caused by a maternal illness. But even after controlling for several such illnesses, the association between mothers taking acetaminophen during pregnancy and asthma in their offspring was still observed. Whether mothers took a medication for pain, fever, or a respiratory tract infection, there was a small increased risk of her child having asthma by age 3. The only condition in the mother that had an association with asthma in the child was pain, even if she did not use acetaminophen.
Similarly, the researchers tried to minimize the possibility that it was respiratory infections during infancy that caused the increased risk of asthma rather than the acetaminophen use.
This all sounds very serious, and the very large size of this study makes it important, but the increase in risk of asthma is still rather small. “Based on this modest increased risk, there is no need to be concerned if a child has been exposed,” said the lead author, Maria C. Magnus, of the Norwegian Institute of Public Health, in an interview with The New York Times’ Well Blog. “It might be possible to limit the amount of Tylenol used, but mothers should not be afraid to use it when necessary.”
According to the Centers for Disease Control and Prevention, 65 percent of pregnant women use Tylenol.