One evening in 2019, when I was a pediatrics resident, I admitted a two-month-old to the hospital for observation after a minor surgery. I explained to the baby\u2019s mother that I planned to order acetaminophen\u2014commonly sold over the counter as Tylenol\u2014every six hours, because the baby had an obvious source of pain. If pain still kept the baby from eating, sleeping, or calming down, the mother could ask for an opioid. I was just leaving the room when the mother stopped me to ask about the acetaminophen.<\/p>\n
\u201cDoesn\u2019t it cause autism?\u201d she said.<\/p>\n
\u201cI\u2019m not familiar with any research linking Tylenol to autism,\u201d I told her. \u201cBut I\u2019ll look into it and get back to you.\u201d In the meantime, we agreed to use both the acetaminophen and the opioid as needed, instead of administering them on a schedule.<\/p>\n
When I sat down at a hospital computer, I was surprised to find that the mother\u2019s question had a basis in mainstream research. Small studies had associated acetaminophen exposure in utero with a baby\u2019s risk of developing autism. But this wasn\u2019t the same as saying that Tylenol caused autism. Perhaps whatever the drug was treating\u2014for example, fevers, infections, or painful chronic conditions\u2014contributed to autism, and acetaminophen did not.<\/p>\n
For babies under three months, as for pregnant women, Tylenol is considered the safest medicine for fever. (Ibuprofen and similar medications, NSAIDs, have been associated with kidney injury in babies.) I continued to order it for patients, if a little more cautiously. Then, in 2024, a more rigorously controlled study<\/a> of more than two million children born in Sweden found no connection between acetaminophen and neurodevelopmental disorders. As the epidemiologist Katelyn Jetelina has written, \u201cthe evidence leans heavily towards correlation, not causation. (Tylenol is not the cause.)\u201d<\/p>\n Last week, during a press conference, President Trump contradicted existing research by urging women to \u201ctough it out\u201d and avoid Tylenol during pregnancy. \u201cFight like hell not to take it,\u201d he said. On Friday, he wrote on Truth Social, \u201cDON\u2019T GIVE TYLENOL TO YOUR YOUNG CHILD FOR VIRTUALLY ANY REASON.\u201d Medical groups disagreed. The American College of Obstetricians and Gynecologists (ACOG) advised women to continue using Tylenol when needed. \u201cMisleading claims that the medicine is not safe and is linked to increased rates of autism send a confusing, dangerous message to parents and expectant parents and does a disservice to autistic individuals,\u201d the American Academy of Pediatrics said.<\/p>\n Now doctors are reporting<\/a> that pregnant women are hesitating to use the medicine, even when professionals recommend it for pain or for fever<\/a>. One reason that Trump\u2019s claims are difficult to dispel is that he makes them sound certain. Doctors, in contrast, can say that the strongest research does not show a link between Tylenol and autism, and that medical professionals consider it the best option for pain and fever in pregnancy. But we know that there is uncertainty in medical research, and so we speak with care.<\/p>\n It ought to be possible for doctors to be more definitive. Pregnancy is not a rare condition\u2014millions of people get pregnant each year\u2014yet those who experience it are frequently told that there\u2019s not enough research to guarantee that a medicine is safe. When a pregnant woman needs medicine, whether for lupus or for high blood pressure, she may feel that she faces an impossible choice: suffer through a condition that may itself harm her or her baby, or else allow an uncontrolled experiment inside one\u2019s own body. Isn\u2019t there a better way?<\/p>\n Many of the rules that govern research on human beings date back to the Nuremberg Code, a response to Nazi doctors who conducted brutal experiments in concentration camps. To this day, research participants must consent; trials must be stopped if there is evidence of substantial harm. In the nineteen-sixties, the public became aware that thalidomide, a widely used nausea drug, had caused birth defects in an estimated eight thousand children outside of the United States. The drug became a case study for the growing field of bioethics. In 1977, the F.D.A. excluded not only pregnant women but also women \u201cof childbearing potential\u201d from early-stage clinical trials, which focus on safety and toxicity. Drugs are instead tested for toxicity in pregnant animals\u2014usually, rats and rabbits\u2014which often respond very differently than humans<\/a>.<\/p>\n According to Ruth Faden, the founder of the Johns Hopkins Berman Institute of Bioethics, these efforts to protect women and babies had unintended consequences. In fact, she said, public responses to thalidomide were a \u201cmisreading of history.\u201d Thalidomide wasn\u2019t systematically tested on pregnant women. If it had been, then its risks likely would have been discovered sooner, and fewer children would\u2019ve been affected.<\/p>\n