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In a press conference totally divorced from reality as scientists and doctors understand it, President Trump announced yesterday that the FDA would be warning providers and patients away from acetaminophen (such as Tylenol) in pregnancy. There were some other unsubstantiated claims about vaccines and autism mixed in, so let me break down what’s actually known and understood here.
What is acetaminophen?
Acetaminophen is an over-the-counter medication used to relieve pain and fevers. The flagship products of the Tylenol company are acetaminophen pills and syrups, but Tylenol sells other products as well, including medicines with a mixture of active ingredients. (Always check the Drug Facts label when you take medications to know what you’re getting.) I’ll often use the word Tylenol, since it’s more commonly known, but acetaminophen is also available in other products, like Excedrin and NyQuil..
Outside the U.S., acetaminophen is often known as paracetamol: Same drug, different generic name, though Trump seems to have stuck with the brand name Tylenol during the press conference. The Tylenol company now has a pop-up on its website pointing customers to this response, which correctly points out there is no credible link between Tylenol and autism.
What the science actually says about acetaminophen and autism
The short answer: There is no credible link between autism and the use of acetaminophen in pregnancy. But HHS Secretary Robert F. Kennedy, Jr. sorta-kinda spoke correctly when, during the press conference, he said there were some studies that “suggest a potential” connection between acetaminophen and autism. For example, a review published this year (not a study itself, but an analysis of prior studies) found that some studies do in fact show a link between acetaminophen use in pregnancy and autism, although the evidence is mixed.
A press release about the review noted, “While the study does not show that acetaminophen directly causes neurodevelopmental disorders [emphasis mine], the research team’s findings strengthen the evidence for a connection and raise concerns about current clinical practices.” That said, it seems most medical experts aren’t convinced that this review, or the studies that claimed to find a link, are strong enough to change clinical practice. (More in the next section on what medical experts are saying about these claims.)
So why doesn’t this count as strong evidence? An association (two things tend to occur together) is not the same as causality (this thing definitively causes that thing). People who take acetaminophen during pregnancy tend to be different than those who don’t—for example, if somebody takes Tylenol during pregnancy because they are sick, it may be the sickness rather than the Tylenol that is the risk factor. Or the people who take Tylenol may be different from people who don’t in some other way.
A large study published last year took this into account. The researchers looked at 2.5 million children in Sweden, and their initial analysis found an increase in risk of autism in children whose mothers had taken acetaminophen. But then they looked at whether this relationship held up between pairs of siblings, where one was exposed to acetaminophen in utero and the other was not. And the relationship disappeared.
In other words, if acetaminophen increased autism risk, you’d expect the sibling exposed to the drug in utero to have a higher likelihood of autism than their sibling who wasn’t. But that wasn’t the case. Instead, it seems some families have a higher likelihood than others of having children with autism, and taking acetaminophen doesn’t increase the risk within that family.
What medical experts say about acetaminophen in pregnancy
Acetaminophen (including Tylenol) is generally considered the safest pain reliever for use in pregnancy. Other common alternatives, like ibuprofen, have known risks and are not recommended if you are able to take acetaminophen instead. Medical experts also agree that it’s dangerous to leave pain and fever untreated during pregnancy.
Several medical organizations issued statements in response to the president’s press conference, all of which are worth reading in full, but here are some key quotes from each:
The American College of Obstetricians and Gynecologists said in a statement: “Suggestions that acetaminophen use in pregnancy causes autism are not only highly concerning to clinicians but also irresponsible when considering the harmful and confusing message they send to pregnant patients, including those who may need to rely on this beneficial medicine during pregnancy.” The statement goes on to discuss the strength of the evidence, saying that “not a single reputable study has successfully concluded that the use of acetaminophen in any trimester of pregnancy causes neurodevelopmental disorders in children.”
The Society for Maternal-Fetal Medicine said in their statement: “In response to today’s White House press conference announcement, the Society for Maternal-Fetal Medicine (SMFM) reiterates its recommendation advising both physicians and patients that acetaminophen is an appropriate medication to treat pain and fever during pregnancy. Despite assertions to the contrary, a thorough review of existing research suggesting a potential link between acetaminophen use during pregnancy and an increased risk of autism and attention deficit and hyperactivity disorder (ADHD) in children has not established a causal relationship.”
What do you think so far?
The American Academy of Pediatrics said in their statement: “Today’s White House event on autism was filled with dangerous claims and misleading information that sends a confusing message to parents and expecting parents and does a disservice to autistic individuals. … Families who have questions about their child’s medications, autism care plans or other health care should consult with their pediatrician or health care provider.”
The Autism Science Foundation said in their statement: “Any association between acetaminophen and autism is based on limited, conflicting, and inconsistent science and is premature… Today’s announcement distracts from the urgent scientific work needed to understand the true causes of autism and to develop better supports and interventions for autistic people and their families.”
The European Medicines Agency, which plays a similar role in Europe as the FDA does in the U.S., issued a statement that there is no new evidence that would require reevaluating the status or labeling for acetaminophen, which they call paracetamol. “Paracetamol remains an important option to treat pain or fever in pregnant women. Our advice is based on a rigorous assessment of the available scientific data and we have found no evidence that taking paracetamol during pregnancy causes autism in children.”
There is no evidence that vaccines cause autism, either
The press conference also repeated long-debunked myths about vaccines and autism. There’s no credible link here, either to vaccines in general, to specific vaccine ingredients like mercury, or to combined vaccines like the MMR (measles-mumps-rubella vaccine).
And I shouldn’t have to tell any parent this, but babies are not in fact “pumped” with a “vat” of “80 different vaccines” at “one visit,” as Trump claimed. Babies see the pediatrician every few months during their first year of life, getting a few shots each time, many of which are combination vaccines (not just the MMR). Many of these vaccines need to be given in multiple doses—it’s not a one-and-done shot for each one.
So it’s not true that separating the MMR into its components has “no downside.” Splitting the shots means kids are getting more needle sticks and delaying the date at which they’ll get their last dose of each and be fully protected. (The CDC’s vaccine advisory panel, which was gutted of its longtime experts and filled with controversial replacements handpicked by the HHS secretary, who has long been an anti-vaccine activist himself, has already voted to remove the combined MMR-chickenpox vaccine as a standard option for young children.)
Trump also repeated the myth that there’s no reason for babies to get hepatitis B shots at birth. Hepatitis B can be sexually transmitted, sure, but it’s not only sexually transmitted. Babies can get it at birth from a parent who doesn’t know they have it; they can also get it during childhood from various non-sexual, non-drug exposures. Hepatitis B is a more severe disease the younger you get it, and it’s one of the vaccines babies’ immune systems can process even in those early days (not all vaccines will work that early) so the risk-benefit calculation is an easy one: this vaccine, like others, offers children real protection.
