Tylenol and Autism

I have often quoted Santayana as saying: “Those who cannot remember the past are condemned to repeat it.”

When I was a resident, there was a thought that too much oxygen caused premature infants to develop blindness. There was a flurry of lawsuits involving patients who became blind.

I actually was named in one of those lawsuits as a resident. I had a patient that the oxygen mixer broke one night. I was in a small hospital with only one oxygen mixer. My choice was to give 100 percent oxygen or room air. On room air, the patient’s pulse oxygen dropped to unsatisfactory levels and the heart rate dropped in half.

I had to continue the 100 percent oxygen to save her life. She ultimately developed blindness. Thus, the lawsuit. We later found out that oxygen was just one of many factors so that there was not a direct relationship. The lawsuits stopped.

In the mid-20th century, there was a drug called Bendectin. It was very effective for morning sickness in pregnancy. Many patients had taken it effectively. At one point patients who later had infants with brith defects tried pointing the finger at Bendectin as the culprit.

Lawsuits followed. Most of them were settled. However, it ultimately reached a point where the company was losing more money on the lawsuits than it was making on Bendectin. In 1983, they discontinued it. In 1994, the studies were released proving that Bendectin had not caused the birth defects. By then it was too late for pregnant mothers to be able to use an effective drug.

We have long known that fever in pregnancy is a bad thing. It causes an increased risk for spina bifida, congenital heart disease, cleft lip and abdominal wall defects. It is particularly bad in the first trimester.

One of the other links to fever in pregnancy is the fact that it appears to increase the risk of autism. That is especially true if the fever occurs in the second trimester. Risk for autism increases by 40 percent in that situation. The risk is higher if the fever lasts for a longer time. The risk is higher if there are recurrent fevers. But the risk is only statistical and not proven.

There also appears to be a statistical and not proven risk that the use of Tylenol (acetaminophen) during pregnancy may increase the risk for autism. However, the theoretical increased risk is so small, it does not explain the high rate of autism in the population. Of course, if the Tylenol is taken for a fever, then the fever alone presents more of a risk.

So, which is the greater risk – fever or Tylenol? By the time we find out, the legal system may have settled the argument like it did for oxygen and Bendectin.

As of March 2025, there were over 100 lawsuits already filed against Tylenol manufacturers. There was a class action lawsuits filed on behalf of parents of autistic children in New York. If we later find out that the information was wrong, it might be another instance of “Oh well”. Santayana may rise up from his grave to say, “I told you so.”