There is a lot of uncertainty when it comes to whether or not pregnant women can take over-the-counter pain relievers. While many doctors advise against the use of ibuprofen and aspirin during late pregnancy, acetaminophen-based relievers like Tylenol are typically thought of as safe — so much so that the CDC reports an estimated 65 percent of pregnant women in the US take it. But a recently released study has found a shocking link between the use of acetaminophen during pregnancy and speech delays in some babies.
The study, conducted by the Mount Sinai School of Medicine and published in the European Psychology journal, interviewed 754 Swedish women who were eight to 13 weeks pregnant. The women were asked questions about how often they used acetaminophen — the active ingredient in Tylenol and other meds — during their pregnancies, and they were asked to provide urine samples in order to have their acetaminophen levels checked.
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Later, when the women had given birth and their children reached 30 months old, scientists gave the women's children language-development assessments, then compared the scores to the frequency of their mothers' acetaminophen use during pregnancy. Shockingly, researchers found that 10 percent of the children they assessed had a language delay, which is described in the study as "children who use no more than 50 words" at 30 months.
While boys, on average, are more likely than girls to have speech delays, the study actually found no link between an increase in the number of boys with speech delays and their moms' acetaminophen use. But girls whose mothers took high amounts of acetaminophen while pregnant were almost six times more likely to have a language delay than girls whose mothers took none. Essentially, the more acetaminophen moms took, the more likely it was that their daughters would experience a language delay.
Time reports that researchers aren't entirely sure why acetaminophen has different effects on male and female babies. They theorize that the differences may be because girls at 30 months tend to have better vocabularies, on average, than boys at 30 months. Acetaminophen use may simply diminish the "female advantage," meaning speech delays may appear as more prevalent in girls because they're expected to have a better vocabulary.
While this study is the first exploring the link between prenatal use of acetaminophen and language delays, it isn't the first to explore the effects the drug could have on unborn children. A 2016 study conducted at the University of Bristol also found that women who take acetaminophen during pregnancy are more likely to have kids with behavioral issues and hyperactivity.
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These revelations are troubling because, as researchers in this most recent study discovered, acetaminophen use during pregnancy is exceptionally common. As many as 59 percent of the women involved in the study admitted taking it at least one time during their first trimester. Others revealed they had taken up to 100 pills in the same time frame.
"Given the prevalence of prenatal acetaminophen use and the importance of language development, our findings, if replicated, suggest that pregnant women should limit their use of this analgesic during pregnancy," said the study's author, Shanna Swan, PhD, professor of environmental and public health at the Icahn School of Medicine at Mount Sinai. "It's important for us to look at language development because it has shown to be predictive of other neurodevelopmental problems in children."
Issues with language development — specifically speech delays — have been known to be indicators of autism. They can also be early indicators of things like auditory processing disorder, a disorder that affects how the central nervous system uses auditory information, and language-based learning disabilities. Studies have shown that many children who have language delays at 24–30 months end up catching up with their peers at around 3 to 4 years old.
While researchers don't want moms to panic, they do want them to consider the results carefully and talk with their doctors. "What we want to tell women is, first of all, to consult your physician before taking any medication — over-the-counter or not — during pregnancy," said Swan. "And second, take as little of it as possible, and only when medically indicated."
