For decades, moms have trusted acetaminophen as the go-to pain reliever and fever reducer for their children. They’ve even used it for themselves when they are pregnant. According to regulatory agencies and what is considered common knowledge to most pregnant women:
It is classified as category B for safety in pregnancy (no risks have been found in humans) by the US Food and Drug Administration and is widely considered the drug of choice for fever and pain in pregnant and lactating women.1
According to WebMD:
Two-thirds of American women take acetaminophen for the aches and pains of pregnancy.2
But was that trust misguided?
Following the Science
A study from John’s Hopkins University, and published by Oxford Academic’s American Journal of Epidemiology, reveals that prolonged in utero exposure to developing babies is related to an elevated risk of ADHD and ASD (Autism Spectrum Disorder).
"People in general believe Tylenol is benign, and it can be used safely for headaches, fever, aches, and pains," says Xiaobin Wang, a professor in the Bloomberg School's Department of Population, Family, and Reproductive Health and the study's corresponding author. "Our study further supports the concerns raised by previous studies—that there is a link between Tylenol use during pregnancy and increased risk for autism or ADHD."3
In 2014, researchers had harsh criticism for acetaminophen (paracetamol in other countries) and called its safety into question. According to an article published on the NIH’s PubMed website:
Acetaminophen/paracetamol is the most widely used drug of the world. At the same time, it is probably one of the most dangerous compounds in medical use, causing hundreds of deaths in all industrialized countries due to acute liver failure (ALF). Publications of the last 130 years found in the usual databases were analyzed.
… may cause not only ALF and kidney damage but also impaired development of the fetus and the newborn child. It appears timely to reassess the risk/benefit ratio of this compound.4
The FDA does not review, approve, or evaluate OTC (over the counter) drugs. According to the FDA’s website on drug product applications:
Disclaimer: Most OTC drugs are not reviewed and approved by FDA, however they may be marketed if they comply with applicable regulations and policies. FDA has not evaluated whether this product complies.5
Acetaminophen, ADHD, and Autism
Acetaminophen has been shown to pass through the placenta. If mom is taking acetaminophen, so is baby. In animal trials, acetaminophen has been shown to affect brain cells and hormones that can impact brain development.6
Xiaobing Wang, M.D., of the Johns Hopkins University Bloomberg School of Public Health, Baltimore, conducted one long-term study. Umbilical cord blood from 996 births were collected and the data was compared with the child development nearly 8.9 years later. Here are the results:
- 8% had been diagnosed with ADHD only
- 6% had been diagnosed with ASD only
- 2% had been diagnosed with ADHD and ASD7
As the amount of acetaminophen and its byproducts increased in the cord blood, so did the risk.
The odds of these developmental disorders were more than twice as high in children exposed to acetaminophen near the time of birth.6
Chief of developmental and behavioral pediatrics at Cohen Children's Medical Center, in New Hyde Park, N.Y., Dr. Andrew Adesman, also voiced concerns:
"Although acetaminophen is a very safe and effective medication when taken as recommended in general, it may not be as safe as presumed if it is taken during pregnancy," he said.
"Since we do not know when during pregnancy the neurodevelopmental risks of acetaminophen exposure are greatest, it is hard to counsel pregnant women as to when they may safely take this medication without increasing the likelihood of their child having ADHD or [autism]," he added.6
According to study reports published on The American Journal of Epidemiology:
Several studies have evaluated acetaminophen’s potentially neurodisruptive properties. Recent studies reported that acetaminophen has (in rats) direct neurotoxic toxic effects in cortical neurons.
These studies have reported that even small doses of acetaminophen may affect neurodevelopment and that this effect is sometimes apparent years after exposure. Such information is cause for significant concern, given the common use of acetaminophen during pregnancy and the sharp increases in incidence of ADHD and ASD.1
Not Just in Utero
In 1980, the CDC started warning parents against using aspirin for children. This recommendation was effective in driving sales away from children’s aspirin and replaced with sales of acetaminophen.8
The NIH has expressed its concern regarding this transition away from aspirin and to acetaminophen:
We have shown that the current rise in cases of autism began in 1980 in the US, which is the same year that the CDC warned against the use of aspirin in US children. There is no good evidence that acetaminophen is superior to aspirin for use in children, and we have shown evidence that acetaminophen use is associated with ASD. We recommend that the use of acetaminophen in children be reviewed for safety.8
The study went on to say that it recognized that it was able to link acetaminophen use of children, including young infants and toddlers to an autism diagnosis after normal development.
Recently it has been shown that more than half of ASD cases are attributable to environmental factors. A subset of children with ASD undergo a period of apparently normal development followed by a regression in development. Since children with regression in development did not initially manifest ASD features, they may have been more likely influenced by drugs or other environmental exposures. In our own data, regression was featured in 38% of cases, and we were able to show an increased likelihood for ASD from acetaminophen use, which was higher in children with regression. Prenatal and perinatal use of acetaminophen, also known as paracetamol, was linked to ASD in an ecological study.8
…younger children with ASD compared to control children were significantly more likely to use acetaminophen at 12–18 months of age and after the MMR vaccination.
The use of pain relievers and fever reducers for young children can be high when considering teething, fevers, vaccinations, and other illnesses or injuries. It is easy to see how acetaminophen could be frequently used and likely overused.
Not Just ADHD and Autism
In a recent Nature article, it is apparent the concern isn’t limited to the U.S. nor ADHD and autism. In a publication under the consensus statement section from September of 2021, a group of scientists, doctors, and researchers call for a “precautionary action” of the use of paracetamol, an international name for acetaminophen.
Furthermore, in Western regions the prevalence of male reproductive and urogenital disorders has increased. These disorders include cryptorchidism, hypospadias and testicular germ cell cancer, together with early puberty, decreased sperm counts, levels of sex hormones and decreased fertility. Data support the contribution of environmental exposure during fetal life, including exposure to pharmaceuticals, to these increases in rates of neurological, urogenital and reproductive disorders.9