A new study has linked aspirin and acetaminophen to cerebral palsy.
According to researchers from the University of Copenhagen, an analysis of nearly 190,000 mother-child pairs found that women who took aspirin at least once during pregnancy were more than twice as likely to deliver children with bilateral spastic cerebral palsy. Increased risks for a unilateral form of the neuromuscular disorder were also observed for acetaminophen, the active ingredient in Tylenol.
Scientists Worry About Common Drugs In Pregnancy
As researchers from the University of Copenhagen write in their new paper for the International Journal of Epidemiology, scientists have expressed concern in the past that mild painkiller drugs may be able to affect brain and spinal cord development in unborn children. The main problem, as you might expect, is that some women use low-dose analgesic medications during pregnancy.
The use of aspirin is generally discouraged in pregnant women, the Mayo Clinic says, since it can harm fetal development. That’s especially true at higher doses. Lower doses of aspirin, on the other hand, are occasionally recommended to pregnant women who have blood clotting disorders, develop preeclampsia or have lost three or more consecutive pregnancies in the past.
Majority Of Pregnant Women Take Tylenol
More common is acetaminophen (referred to outside the United States as paracetamol), the active ingredient in Tylenol. Doctors have been prescribing Tylenol to pregnant women for decades, since the drug is generally considered safe for developing children.
It’s no surprise then that a 2014 review in the British Medical Journal estimated that between 65% and 70% of pregnant women in the United States use acetaminophen.
This widespread use has worried a number of medical researchers.
Despite Concerns, No Proof Of Cerebral Palsy Link
Over the last five or so years, interest in reassessing the pregnancy safety of drugs like Tylenol and aspirin has grown. Most of this research has focused on acetaminophen, because it’s usually the drug recommended to pregnant women in the first place. And, to date, scattered medical reviews have linked Tylenol, when taken during pregnancy (usually the first trimester), to a number of medical conditions in children, including ADHD, autism spectrum disorders and asthma.
The evidence, though, is mixed, says Dr. Hal C. Lawrence, executive director of the American College of Obstetricians and Gynecologists. Speaking to WebMD in 2016, Lawrence reassured parents that studies “show no clear evidence that proves a direct relationship between the prudent use of acetaminophen during any trimester and developmental issues in children.”
Danish Study Takes On Painkiller Controversy
Hoping to clarify things, a team of Danish public health researchers, with help from epidemiologists at UCLA, set out to study the issue using Scandinavia’s remarkably-thorough birth records.
Compared to the United States, countries like Denmark and Norway maintain exquisite medical health registries, probably because both countries have nationalized health systems. Whatever the reason, most extremely-large studies on pregnancy emerge from Scandinavia. Having accurate medical and birth records allows scientists to access the data they need efficiently.
185,617 Mother-Child Pairs
The group first collected data from the Danish National Birth Cohort, a study of around 100,000 women and their children, and the similarly-structured Norwegian Mother and Child Cohort Study. In the end, a total of 185,617 pairs of mother and children were included. Then, using medical records, the authors divided those mothers who had taken an analgesic during pregnancy from women who hadn’t:
- 49% used acetaminophen at least once during pregnancy
- 3% used aspirin at least once during pregnancy
- 4% used ibuprofen at least once during pregnancy
After that, they identified all of the children who had been diagnosed with some form of cerebral palsy, which came to a total of 357 babies. To finish off, the team used statistical models to figure out whether women who used a painkiller in pregnancy were more likely to give birth to children with the neuromuscular disorder.
Acetaminophen: 30% – 60% Increased Risk
Women who used acetaminophen at least once were around 30% more likely to have kids who were subsequently diagnosed with cerebral palsy. The risk appeared to be highest for cases of unilateral spastic cerebral palsy, the authors say, noting a 50% increased risk. That subtype of the condition, associated with prenatal brain damage, affects only one side of a child’s body.
The risk for unilateral cerebral palsy disorders was increased further, up to 60%, when a child was exposed to Tylenol during the second trimester, a crucial period for brain development.
Aspirin: 240% Increased Risk
Even more troubling results came when the team turned to aspirin. Children who were exposed to aspirin during pregnancy were more than twice (2.4-times) as likely to develop bilateral spastic cerebral palsy, which affects muscles on both sides of the body, than unexposed children.
Importantly, the researchers controlled for a number of confounding factors. Painkillers, after all, are taken to control pain or fever, underlying medical conditions. It’s possible that any one of these preexisting factors could be driving the observed increase in cerebral palsy cases. In that case, the problem wouldn’t be with acetaminophen or aspirin, but the medical conditions for which they are often prescribed.
Researchers can use statistical models to “control” for these potential confounders, which might be muddying up their findings. And, while the authors say they “controlled for several important indications for analgesic use,
Commenting on the results for the Daily Mail, Dr. Sunit Godambe told reporters that, while the Danish study was very large, it couldn’t prove a causal association between any drug and cerebral palsy. “However, all medication in pregnancy should only be taken once a doctor has been consulted,” the physician, who was not involved in the study, concluded.