Association of maternal asthma with congenital heart defects in offspring

Introduction Asthma is the most common chronic disease among pregnant women. Some studies have linked maternal asthma to an increased risk of congenital malformations, particularly congenital heart defects (CHDs). Among these, ventricular septal defect (VSD) is the most common, accounting for nearly half of all CHD cases. We investigated the association between maternal asthma and the risk of CHD in offspring. As a sensitivity analysis, we also examined the associations between maternal atopic predisposition, maternal use of asthma medication, and CHD risk. Material and Methods This retrospective, population‐based study utilized a comprehensive birth cohort of all singleton births in Finland between 1996 and 2018. Data were derived by linking four high‐coverage national health registers. Results The cohort included 1 274 540 eligible mother–child pairs. A total of 106 544 (8.4%) mothers had a diagnosis of asthma or had purchased asthma medication during pregnancy. Of the offspring, 18 772 (1.5%) were diagnosed with a congenital heart defect (CHD), and 8855 (0.7%) had a diagnosis of ventricular septal defect (VSD). Maternal asthma was weakly associated with overall CHD (OR 1.18; 95% CI, 1.12 to 1.24) and with VSD (OR 1.19; 95% CI, 1.10 to 1.27). The association between maternal asthma and CHD was observed in both allergic asthma (OR 1.33; 95% CI, 1.18 to 1.50) and nonallergic asthma (OR 1.27; 95% CI, 1.04 to 1.56). Maternal allergic conditions, such as atopic dermatitis and allergic rhinitis, were also associated with CHD overall (OR 1.13; 95% CI, 1.02 to 1.25) and with VSD (OR 1.20; 95% CI, 1.04 to 1.38). Conclusions Maternal asthma and allergic tendency are associated with a modestly increased risk of CHD in offspring, particularly VSD. Nonallergic asthma was also linked to CHD, especially right‐sided defects. These findings suggest that maternal allergic inflammation may have teratogenic effects during fetal cardiac development.