Paracetamol or other painkillers taken during pregnancy are unlikely to cause asthma in the child, according to a large study by researchers at Karolinska Institutet and Queen Mary University of London. The study, which is published in the European Respiratory Journal, suggests that there is another factor linked to use of these drugs that increases the risk of asthma.
The analysis includes prescription data on painkillers for almost 500,000 Swedish mothers. The results support earlier findings that women taking paracetamol during pregnancy are more likely to have children who develop asthma. However, they also suggest that the painkillers are not the cause of this increase.
Children born to mothers who had been prescribed paracetamol during pregnancy had an increased risk of asthma, but the risk was similar when women had been prescribed different types of painkillers that work in different ways, such as opioids or migraine medication. For example, the increase in risk for asthma at five years of age was 50 per cent for paracetamol, 42 per cent for codeine and 48 per cent for migraine medication.
The results suggest that another factor linked to use of these drugs is responsible for the increase in asthma risk. One explanation could be that women who are taking prescribed painkillers are more likely to suffer from chronic pain or anxiety, or have a propensity to seek health care.
"Severe pain, and the stress that it causes, have profound effects on the body, including on levels of some hormones, and there is evidence for a link between high levels of mothers' stress in pregnancy and increased risk of asthma in the offspring," says Professor Seif Shaheen at Queen Mary University of London, UK, who led the study in collaboration with Professor Catarina Almqvist Malmros and colleagues at Karolinska Institutet.
Researchers say their results should give women reassurance to take painkillers during pregnancy when they are prescribed by a doctor.