Maternal systemic lupus erythematosus during pregnancy is associated with an increased risk for asthma among offspring, and infants born to mothers with SLE who smoked during their pregnancy have the highest risk.

The investigators sought to examine the relationship between maternal SLE in pregnant women and childhood asthma and to explore the role of preterm birth as a mediator of this association via the use of Swedish Lupus Linkage (SLINK) registry data. Information on 12,000 singleton live births between 2001 and 2013 was compiled from SLINK. Childhood asthma was defined as 1 or more International Classification of Diseases-coded visits in the National Patient Register.

Risk ratios (RRs) for asthma were estimated, taking into account any potential confounders. The researchers used mediation analysis to estimate what percentage of the total effect observed can be explained by preterm birth (<37 weeks’ gestation; 17.3% of SLE pregnancies) or moderate preterm birth (<34 weeks’ gestation; 6.1% of SLE pregnancies).