Studies show that acetaminophen from the mother’s blood can cross the placenta and enter the baby’s bloodstream. Acetaminophen is known to change the function of the immune system and the inflammatory response. It may also make cells more sensitive to oxidative stress, which occurs as a result of normal cell metabolism. Researchers believe that these mechanisms could explain how acetaminophen affects fetal brain development. However, research in this field is still ongoing, and it will likely take years to fully understand the impact that acetaminophen has on a developing baby’s brain.