A prospective study of preconception asthma and spontaneous abortion

Purpose: To evaluate the relationships among history of asthma, asthma severity, and spontaneous abortion (SAB). Methods: Pregnancy Study Online is a preconception cohort study of North American couples. During the preconception period, female participants reported their history of physician-diagnosed asthma, age at first diagnosis, and use of asthma medications in the previous 4 weeks. Asthma severity was classified by medication use proximal to conception, from level 0 to 3 in increasing severity. Pregnancy and SAB were identified using data from follow-up questionnaires. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs). Results: Among 6325 participants who conceived, 19% experienced SAB and 17% reported a history of asthma. There was no appreciable association between asthma history and SAB incidence (HR = 0.98; 95% CI: 0.84, 1.14). HRs comparing severity levels 0, 1, and 2-3 with no asthma were 0.82 (95% CI: 0.67, 1.01), 1.20 (95% CI: 0.91, 1.60), and 1.31 (95% CI: 0.97, 1.78), respectively. Among women who conceived without the use of fertility treatment, level 2-3 severity was associated with SAB (HR = 1.39; 95% CI: 1.02, 1.89). Conclusions: While history of asthma diagnosis was not materially associated with SAB, having severe asthma (based on medication use) was associated with greater SAB risk. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

The study found that there was no significant association between a history of asthma and the incidence of spontaneous abortion (SAB), but severe asthma (based on medication use) was associated with a higher risk of SAB.