Acetaminophen Use During Pregnancy Linked With Delayed Language Abilities In Girls

acetaminophen tablets
Tablets of acetaminophen, also referred to as paracetamol, sit on a table on July 24, 2014 in Melbourne, Australia. Scott Barbour/Getty Images

A top-selling painkiller has been linked with serious language delays in a new study published Wednesday. Girls born to mothers who had taken more than six tablets of acetaminophen while pregnant were nearly six times as likely to have spoken fewer than 50 words—less than the vast majority of their peers—by the time they were two and a half years old. This lag could have implications for their long-term language abilities and academic performance.

The study examined data from 700 pregnant women and their children in Sweden and was published in European Psychiatry. Swedish children all go through a routine language screening around 30 months after they're born; parents answer a standard questionnaire, which asks about the number of words that a child has used. More than 90 percent of the children included in this study had spoken more than 50 words by the time they took this assessment.

Acetaminophen is found in products like Tylenol. Medications like these are often used to control a fever, which can be important for pregnant women because a higher than normal body temperature can affect a developing fetus.

But for many medications, over-the-counter and prescription alike, we often don't know how they affect pregnant women or their fetuses. That is true even for medications that have been on the market for years. "It really points out the need to understand these exposures better," Study co-author Shanna Swan told Newsweek.

Swan, who researches environmental and public health at Mount Sinai's Icahn School of Medicine, thinks the link between acetaminophen and language delays in girls may hint at other such problems. "We believe that this may be a canary in the coal mine kind of thing," she said.

Acetaminophen tablets stacked
Acetaminophen tablets, also known as paracetamol, sit on a table on July 24, 2014 in Melbourne, Australia. Scott Barbour/Getty Images

So Much Tylenol

Not all women who take acetaminophen do so for medical reasons, Swan speculated. She recalled a column in the New York Times originally entitled, "For a Broken Heart, Take Tylenol." "So that is how many people take Tylenol—they're depressed, they're anxious, they can't sleep, their kids are bothering them,"she said, "and women take a lot when they're pregnant."

In fact, based on urine samples that Swan and her colleagues collected, every woman had been exposed to acetaminophen or a chemical that was processed into a similar end product called a metabolite. These chemicals, Swan noted, include aniline, sometimes used as a fabric dye. (Swan and her colleagues could tell which of the women had likely taken the medication intentionally and which were likely exposed to it or another chemical in their environment.)

Acetaminophen wasn't always used so much, said Dr. Mady Hornig, an epidemiologist at Columbia University's Mailman School of Public Health who was not involved in the research. But, Hornig noted, it is now. In her work, she found that about 50 percent of women said they'd used some acetaminophen during their pregnancies.

From Aspirin to Acetaminophen

Before the 1980s, Hornig explained, people used aspirin to control fevers in small children. However, doctors began to notice that some children had serious reactions to aspirin. This group of symptoms, which can include diarrhea, sleepiness and even seizures and permanent brain damage, is now known as Reye's syndrome.

As acetaminophen gained favor as the fever medication of choice for children, it also became more popular among adults. "From that change in the pediatric usage, it began to creep into obstetric use and became very widespread as something for pain and fever management," Hornig said. And because acetaminophen has been used for so long, it's generally assumed to be safe.

Dangers have been noted, though. The Food and Drug Administration issued a safety communication in 2015, warning people about the possible risk over-the-counter medications might pose to pregnant women. Taking acetaminophen any time during pregnancy was also associated with an increased risk of attention deficit hyperactivity disorder in children, the agency stated. (There are also questions about acetaminophen's safety in people who are not pregnant, as ProPublica vividly described in 2013.)

Clearly not everyone who takes acetaminophen during pregnancy will give birth to a child with developmental delays. Hornig says genetic differences could influence how mothers and daughters process the drug. The amount of the drug taken also matters, as does the stage of pregnancy when the mother takes the drug.

Swan wonders whether acetaminophen leads to language delays through hormonal changes. But that is only speculation. "We don't know exactly how it would act to affect this particular function of the brain," she says. More research will happen, on this subject and with these specific children, who are now 7 years old.

While that research is ongoing, women who are pregnant or are trying to become pregnant might want to consider reducing how much Tylenol they use. "The take-home message is that one shouldn't be cavalier," Hornig said. "We shouldn't just assume that something is completely safe."