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Women who are pregnant, have children or who are thinking about having children got a scare last week after a new study suggested taking acetaminophen during pregnancy causes children to develop attention deficit hyperactivity disorder (ADHD).
The link certainly seems alarming. And it's not the first time research has warned that painkillers during pregnancy can have damaging consequences. In the past, women have also heard that pain-relieving drugs may lead to a greater chance of miscarriage, birth defects, autism and other serious problems.
Is it any wonder that many women are fearful of taking Aspirin, ibuprofen, acetaminophen or other painkillers while they're pregnant? But is the self-denial of pain-relieving medication justified?
The truth is not what many headlines would have you believe.
Painkillers 101
Generally speaking, there are three classes of over-the-counter painkillers that people take to relieve headaches, joint stiffness, sprained ankles or other run-of-the-mill sources of pain: acetylsalicylic acid, or Aspirin; non-steroidal anti-inflammatory drugs (NSAIDs), such as Advil; and acetaminophen, or Tylenol. Narcotic painkillers, such as codeine, are used less frequently, but may be prescribed to women who have chronic or severe pain.
Tylenol has been the painkiller used by most pregnant women for many years. However, NSAIDs such as Advil have been closing the gap in recent years.
Surveys and research show that many women take pain-relieving medications when they are pregnant. Despite this, there seems to be little consensus among medical authorities or public health officials on the safety of these medications. Do a Google search on painkillers and pregnancy and you'll often find websites offering conflicting advice.
Perhaps that's why any new study that suggests painkillers pose a risk is able to create a large stir. That seems to be what happened with the most recent study linking acetaminophen and ADHD. But a closer look at the study does raise some crucial questions.
A faulty link
In the study, which was published in the journal JAMA Pediatrics, researchers examined the data for nearly 65,000 births in Denmark, as well as prescriptions for ADHD medications and parental reports of behavioural problems.
They found that more than half of the mothers had taken acetaminophen while pregnant and that those who took the medication were more likely to have children with ADHD-like behaviours or a diagnosis of hyperkinetic disorder, a severe form of ADHD.
The researchers warn that because the stakes are so high, more studies are needed to further investigate the link. But there's one rather large caveat that didn't receive its fair share of attention in the media coverage: correlation does not equal causation.
Back in the 1990s, women believed hormone replacement therapy could lower their risk of heart disease, thanks to studies showing those on the drugs enjoyed those benefits. But in 2002, a major randomized controlled trial showed the opposite was true. It turns out the women in the earlier studies had a lower risk of heart problems not because of the medication, but because they were from higher socioeconomic backgrounds.
In other words, just because some women who took acetaminophen had children with ADHD-like behaviours later on doesn't mean the medication caused it. The real explanation could be that those women had a particular lifestyle or trait that explained the slightly raised risk.
Dr. Gideon Koren, director of the Motherisk program at Toronto's Hospital for Sick Children, noted several major flaws in the study that suggest the authors are wrong to conclude acetaminophen leads to ADHD or related behaviour problems. For instance, the researchers didn't ask or take into account whether the parents had those behaviour issues – a significant oversight, considering there is a genetic component to those issues, he said. And women who decide to take acetaminophen for extended periods during their pregnancy may share some problem that could explain the higher ADHD risk.
He highlighted the fact that narcotic painkillers are more complicated. There's no clear evidence linking them to birth defects, but pregnant women who take codeine for long periods could have babies that experience withdrawal symptoms. Health Canada cautions breastfeeding mothers about taking codeine because some women quickly metabolize the drug, which could be harmful to the baby.
Unnecessary suffering
As a result of inflammatory headlines, Koren said he fears women are making unnecessary "martyrs" of themselves.
"There's a huge consensus that she should be effectively treated [for pain] and I do not believe there is any evidence that … will cause problems to the baby," he said. "Now that 75 per cent of women work outside home, the idea of not taking anything and being in bed is not really viable."
Refusing pain relief may also have unwanted consequences. The Society of Obstetricians and Gynaecologists of Canada highlights the fact that "the risk of not taking medication may be more serious than the potential risk associated with taking the medication."
Koren said pregnant women should generally feel safe about taking low doses of medication to treat pain.
Last month, Koren and his colleagues released the results of a study that found women taking NSAIDs such as ibuprofen did not have an increased risk for miscarriage. But only a handful of media outlets covered the story.
Bottom line
All medications come with risks. However, pregnant women shouldn't avoid painkillers because of unfounded fears it will have long-term negative effects on their children.
Koren advises women to speak to their doctor about which painkillers and what doses are appropriate for them – and not to suffer unnecessarily.
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Carly Weeks