Maternal systemic lupus erythematosus (SLE) 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, according to the results of a recent large, nationwide, population-based cohort study conducted in Sweden and published in Arthritis Care & Research (Hoboken).
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). Offspring of mothers with SLE at delivery were 4- to 5-times more likely to be born preterm or moderate preterm. The prevalence of first trimester smoking, obesity, and history of asthma was similar between mothers with and without SLE.
A total of 775 children born to mothers with SLE were compared with 11,225 children born to mothers without SLE. Overall, 13% (97 of 775) of children of mothers with SLE were diagnosed with asthma compared with 11% (1211 of 11,225) of those both to mothers without SLE. The RR for childhood asthma was 1.46 (95% CI, 1.16-1.84). According to the results of mediation analysis, 20% to 29% of the total effect of SLE could be explained by preterm birth.
Maternal smoking during pregnancy was the strongest effect modifier evaluated. The risk for childhood asthma was greater for children born to mothers who smoked (RR, 2.57; 95% CI, 1.32-4.99), those born moderately preterm or preterm (RR, 1.91 [95% CI, 0.94-3.86] and RR, 1.68 [95% CI, 1.09-2.61], respectively), and first-born children (RR, 1.62; 95% CI, 1.18-2.23).
The investigators concluded that prevalent maternal SLE during pregnancy is linked to an elevated risk for asthma among offspring. Although the occurrence of preterm birth can explain some of this association, other unidentified pathologic mechanisms are likely to play a role as well.
Rossides M, Nguyen C, Arkema EV, Simard JF. Asthma in children of mothers with systemic lupus erythematosus and the role of preterm birth [published online November 10, 2017]. Arthritis Care Res (Hoboken). doi: 10.1002/acr.23472