Abstract
OBJECTIVE: Systemic lupus erythematosus (SLE) and asthma share inheritable IgE-related pathophysiology, but the association between maternal SLE and asthma in the offspring has not been explored. Our aim was to investigate the association between maternal SLE during pregnancy and childhood asthma and examine the role of preterm birth as a mediator of the association using Swedish register data. METHODS: Information on 12,000 singleton live births (2001-2013) was collected from the Medical Birth Register. Childhood asthma was defined as at least 1 International Classification of Diseases-coded visit in the National Patient Register. Prevalent maternal SLE at delivery was identified from the Medical Birth Register and the National Patient Register. Risk ratios for asthma were estimated while controlling for confounders. Mediation analysis was used to estimate what percentage of the total effect can be explained by preterm birth (defined as either <34 or <37 weeks of gestation). RESULTS: We compared 775 children born to mothers with SLE with 11,225 born to mothers without SLE. Ninety seven children of mothers with SLE (13%) were diagnosed with asthma, compared to 1,211 in the unexposed group (11%). The risk ratio for childhood asthma was 1.46 (95% confidence interval 1.16-1.84). In mediation analysis, 20-29% of the total effect of SLE was explained by preterm birth. CONCLUSION: Prevalent maternal SLE during pregnancy is associated with an increased risk of asthma in the offspring. While preterm birth can explain a fair proportion of this association, additional unidentified mechanisms also likely play a role.