Maternal Asthma and Adverse Perinatal Outcomes: An Analysis of 434,068 Pregnancies in Canada.

BACKGROUND

Maternal asthma is a known risk factor for asthma and allergic diseases in children. However, there is a lack of data on the role of asthma phenotypes in the association with perinatal outcomes.

OBJECTIVE

To investigate the role of maternal asthma in adverse perinatal outcomes, such as preterm birth (PTB), low birth weight (LBW), and cesarean (C-section) deliveries.

METHODS

This cohort study included all singleton live-birth pregnancies in Alberta between October 2009 and December 2018. Maternal asthma was defined by the International Classification of Diseases codes (ICD-9/10: 493/J45) and was categorized by (1) status: ever (>1 year before pregnancy), current (within 1 year or during pregnancy), and active (during delivery hospitalization) asthma, and (2) phenotypes: high (H) or low (L) blood (B) eosinophil (E) and neutrophil (N) counts. PTB (gestational age at delivery <37 weeks), LBW (≤2500 g), and C-section were the main perinatal outcomes of interest.

RESULTS

Of 434,068 pregnancies, 37,394 (8.6%) women had asthma, of whom 52%, 40%, and 7% had ever, current, and active asthma, respectively. In adjusted analysis, maternal asthma was associated with increased risks of PTB (adjusted relative risk [aRR]: 1.15; 95% confidence interval [CI]: 1.11-1.20), LBW (aRR: 1.11; 95% CI: 1.07-1.16), and C-section (aRR: 1.10; 95% CI: 1.08-1.12), and the risks were highest in active asthma, followed by current and ever asthma. The risk of PTB, LBW, and C-section was higher in the HBE/HBN phenotype, followed by HBN/LBE, HBE/LBN, and LBE/LBN phenotypes.

CONCLUSION

Women with any history of asthma, but particularly those with current and active asthma, are at higher risk of PTB, LBW, and C-sections.