13 January 2014. Foreign chemicals can be detrimental to the fetal brain – even drugs may cause adverse effects. In the past, brain toxicity due to arsenic and methylmercury was in part discovered because they were once used as drugs, though not for long, fortunately. But drugs in general are part of the modern chemical universe, which is foreign to our metabolism. If they pass the placenta, drugs that act on the nervous system (of the mother) are especially likely to present a risk to the developing brain of the fetus (see Only one chance, page 100).
A new study from Norway focuses on paracetamol (acetaminophen in the U.S.), a common painkiller often taken against headaches and other minor aches and pains. This over-the-counter drug is one of the most commonly used drugs. Although generally considered safe when used as intended, excess doses can easily cause liver toxicity. Now we have to think again whether its common use is really all that safe, especially during pregnancy.
The researchers utilized data from the Norwegian Mother and Child Cohort Study, where the mothers had been asked twice during pregnancy on their use of medicines. In such studies, any adverse effects could possibly be due to the disease or ailment of the mother, for which she is taking the drug – so-called confounding by indication. For this reason, the researchers chose to compare siblings of the same sex, so that the mother’s health would be similar in spite of any change in her use of painkillers. In addition, as a separate control, the researchers also used information on the use of ibuprofen, another weak painkiller that is not suspected of toxicity to fetal development.
In the 2919 siblings of the same sex, information was available on psychomotor development and behavior up to age 3 years. After having taken a number of other factors into regard, the message from the data analysis was clear. If the mother had taken paracetamol for more than 28 days, the child had poorer motor development, higher activity levels, and other behavioral problems. The results suggest that the risk of deficits may be as much as doubled when the mother had frequently taken paracetamol during pregnancy. No such tendencies were seen for ibuprofen.
Still, there are some uncertainties. The children’s development was assessed solely on the basis of questionnaire responses. Thus, these findings need to be replicated, preferably by clinical testing of the children. However, this may be difficult to achieve in the short term, as such studies are expensive and take time. Paracetamol has previously been studied in regard to possible adverse effects in the fetus due to maternal use, but most attention so far has been paid to asthma development and risks of malformations.
This new study is yet another reminder that human brain development is extremely vulnerable to foreign chemicals, and any exposure to man-made compounds during pregnancy should be avoided to the extent possible. Given that paracetamol is one of the most commonly used drugs, researchers also need to be aware that exposures are most often complex and usually involve more than one chemical at the time. The brains of today’s children have all been exposed to a fair number of chemical brain drainers, and paracetamol could well be one of them.