March 18, 2019

expert reaction to study on painkillers in pregnancy and asthma

Reactions to research published in European Respiratory Journal that indicates that taking paracetamol during pregnancy is not responsible for increasing the risk of asthma in children.

Prof Jean Golding, Emeritus Professor of Paediatric and Perinatal Epidemiology, University of Bristol, said:

“There are a number of studies that have demonstrated that if the mother takes paracetamol (also known as acetaminophen) in pregnancy, her offspring is at increased risk of developing asthma. Paracetamol is largely bought over-the-counter and not on prescription. Consequently, the only way to determine whether paracetamol has been taken in pregnancy has been by asking pregnant mothers during the pregnancy, often on several occasions. Detailed surveys (birth cohorts) which have taken place in countries such as Norway, Denmark, and the UK find that about 50% of pregnant women have taken paracetamol at some stage. It is using these populations that scientists such as Professor Shaheen have shown the link with asthma in the children. It is likely that half the pregnant women in Sweden will also have taken paracetamol during pregnancy.

“Dr Shaheen’s latest study, about to be published, has taken a different strategy and used prescriptions for paracetamol; these were only given to about 3% of pregnant women. He and his colleagues have shown that women receiving the drug in this way were just as likely to have a child with asthma as were women who had prescriptions for migraine drugs or for opioids.

“In my opinion there is a major flaw in the logic here. The authors of the study do not know whether the women having the other drugs were also taking paracetamol. My guess is that a proportion of them would have also taken paracetamol at some stage. If so, the comparison between the small numbers of women having a prescription for paracetamol with the women taking the other drugs would not be meaningful. In addition, the comparison control group who did not have any of these prescriptions would have included a large proportion who had taken over the counter paracetamol. The consequence is that any true effect of prenatal paracetamol would have been hidden by this study design. Consequently, on the basis of all the other studies I don’t feel that we can state that paracetamol does not cause asthma.”

‘Prescribed analgesics in pregnancy and risk of childhood asthma’ by Shaheen et al. was published in European Respiratory Journal at 00:01 UK TIME Monday 18 March 2019.

Declared interests

Prof Jean Golding: “No conflicts of interest.”