A new study shows that children born to women who take heartburn medicines when pregnant are at least a third more likely to develop asthma symptoms compared with children born to non-users, but scientists say more research is needed to confirm whether the association is causal or if there are any other reasons behind the possible link.
Reporting in the Journal of Allergy and Clinical Immunology
(online, 9 January 2017), the authors say: “Our findings of increased risk may reflect a true risk or may be explained by residual confounding and/or confounding by indication.
“Although we cannot recommend any changes to the use of acid-suppressive medications by expectant mothers, further research is needed, particularly through mounting pharmacovigilance studies, which may prove more ethically acceptable and feasible than initiating randomised controlled clinical trials.”
Led by Rebecca Devine from the department of public health at the NHS Borders Headquarters at the Borders General Hospital in Melrose, Scotland, the researchers based their conclusions on a review of eight studies in five countries which considered asthma symptoms in children born to mothers who had taken acid suppressive medications while pregnant.
They found that children of mothers who used any acid suppressive medications during pregnancy were at an increased risk of asthma symptoms of at least a third compared with non-users (risk ratio, 1.36).
The results were similar when histamine-2 (H2)-receptor antagonists and proton pump inhibitors were examined separately. The results for H2-receptor antagonists showed a hazard ratio of 1.46, while the hazard ratio for proton pump inhibitors was 1.30.
Dosage, pregnancy trimester, and frequency of exposure to acid-suppressive drugs were reported differently across the eight studies, therefore the researchers were prevented from comparing the influence of those factors.
Commenting on the findings, Samantha Walker, director of policy and research at the patient charity Asthma UK, says: “We don’t yet know if the heartburn medication itself is contributing to the development of asthma in children, or if there is common factor we haven’t discovered yet that causes both heartburn in pregnant women and asthma in their children. The study points us towards something that needs further investigation.”
Also commenting on the study, Jean Golding, emeritus professor of paediatric and perinatal epidemiology at the University of Bristol, says it may be the heartburn itself rather than the drugs taken which is associated with an increased asthma risk. “In order to test this, the appropriate comparison should be with offspring of women who have heartburn but do not use medication to treat the condition,” she says.
“This study has not addressed this important possibility, and therefore cannot claim to have demonstrated a causal connection.”
Seif Shaheen, clinical professor of respiratory epidemiology at Queen Mary University of London, says the study confirms other research which has also suggested a similar link, but fails to “shed further light on where this association is likely to be causal or not”.
“Advice to pregnant women does not need to change on the back of these latest data, which should be interpreted with caution,” he says. “For now we should assume that the link is not causal and pregnant women should be reassured.”
 Devine RE, McCleary N, Sheikh A et al. Acid-suppressive medications during pregnancy and risk of asthma and allergy in children: A systematic review and meta-analysis. Journal of Allergy and Clinical Immunology. doi: 10.1016/j.jaci.2016.09.046