On Feb 24, 2014, the JAMA of Pediatrics released the results of a Danish study that may link acetaminophen (the active ingredient in brands such as Tylenol and others) use during pregnancy and ADHD like behavior in children later on. Although correlation does not necessarily mean causation, the authors of the study do suggest that the results of their study are of public concern and further investigation is needed.
Between 1996 and 2002, 64,322 children along with their mothers were enrolled in the Danish study. More than half of the mothers reported using acetaminophen during pregnancy. The results concluded that the children that were exposed to the drug were at much higher risk of being diagnosed and treated for Hyerkinetic Disorders and/or ADHD like behavior by age 7.
Even though further investigation is recommended, it would be safe to say that while pregnant, women should be very cautious as to what drugs they use due during pregnancy as well as what they take while breast feeding since the drug can be found in the breast milk as well. This is due to the fact that many drugs do cross the blood brain barrier and go straight to the infant.
It probably should come as no surprise that acetaminophen may cause such a risk since other health risks of taking the drug have been published now for quite some time. But this is one of the first studies that are showing tremendous potential health risks long term for a child.