How misleading statements on acetaminophen leave expectant parents confused, fearful and lacking in options

When President Donald Trump adamantly proclaimed in a press conference on September 22, 2025, that pregnant women should not take Tylenol, I immediately thought about my own experiences during my second labour. While pushing for nearly three hours, I developed an infection in my uterus called chorioamnionitis, which occurs when bacteria infect the uterus, placenta and sometimes the baby's bloodstream.

I had a fever, and my baby's heart rate was significantly elevated. I remember feeling delirious; my colleague and friend, while delivering my baby, said she had never seen me in such a state. I couldn't focus on pushing. I felt faint, and I worried about my baby.

And I remember the incredible relief that acetaminophen, the active ingredient in Tylenol, brought me when it lowered my fever and decreased my and my baby's heart rate. After taking it, I was able to push with confidence and welcome my healthy daughter, who is now 7 and thriving.

As a practicing obstetrician and medical researcher with nearly two decades of experience taking care of pregnant patients, I have to make a dozen decisions about acetaminophen use on any given day when I am working in the hospital. I have examined the data as a researcher, clinician and educator.

Central to our jobs is balancing the risks and benefits of any treatments. The president's words will not change how I practice, but I worry they will sow confusion in my patients and create fear of potential lawsuits for all practicing health care providers.

The American College of Obstetricians and Gynecologists, the leading organisation that guides medical decisions on pregnancy and childbirth, has reiterated the safety and efficacy of acetaminophen use during pregnancy in light of the confusion surrounding Trump's claims.

Mixed messages I first looked into the data on the possible links between acetaminophen and developmental disorders a few years ago when I received a call from a woman who had recently learned she was pregnant and had caught the flu from her toddler child. She was concerned that Tylenol was dangerous for her developing baby.

Some studies do suggest links between acetaminophen use in pregnancy and neurodevelopmental disorders such as attention deficit hyperactivity disorder and autism. But they lack a crucial distinction. For one, they cannot pin down whether acetaminophen use during pregnancy itself was associated with the neurodevelopmental conditions in the child, or whether the fevers and other symptoms that led people to use the painkiller were playing a role in the outcome.

Secondly, because those studies are based on statistical associations rather than controlled experiments, they cannot show cause and effect. Since it is both unethical and nonfeasible to perform a controlled study evaluating the actual risks of acetaminophen use, the best proxy to control for environmental or genetic factors is to look at maternal exposure to acetaminophen and outcomes of more than one child in individual families.

That's exactly what was done in a 2024. Swedish study that analysed nearly 2.5 million children born from 1995 to 2019 in Sweden to mothers who had documented use of any medication during pregnancy.

When looking at individual children, the researchers found up to a 5% increase in autism for those exposed to acetaminophen during pregnancy. However, when siblings were included in the analysis – controlling for environmental, medical and genetic factors that could have contributed – the small, elevated risk disappeared.

Fever during pregnancy is dangerous for mother and baby. There are many important reasons why doctors like me may recommend acetaminophen to a pregnant patient. One pregnant patient I treated who had the flu was so sick that she was septic, meaning an infection had spread throughout her body. Her 103-degree fever and dangerously low blood pressure threatened her and her fetus's life.

My colleagues and I did not hesitate to treat her with acetaminophen. Our goal was to bring down not only her body temperature but also the fetus's heart rate, since a high heart rate can place dangerous stress on the fetus.

(Author is from University of California)