Timing of Maternal Asthma Diagnosis in Relation to Adverse Perinatal Outcomes

J Allergy Clin Immunol Pract. 2020 Jun;8(6):1938-1946.e4. doi: 10.1016/j.jaip.2020.01.048. Epub 2020 Feb 1.


Background: It is unclear if asthma diagnosed during pregnancy puts the fetus at a higher risk of poor perinatal outcomes than pre-existing asthma.

Objective: To assess if the risks of prematurity, major malformations, and small-for-gestational age (SGA) are higher in women with asthma diagnosed during versus pre-pregnancy.

Methods: We retrospectively analyzed a cohort of pregnant women aged ≥15 years with and without incident asthma, constructed from health administrative databases. Follow-up began 24 months before pregnancy onset (cohort entry) and ended at delivery. Incident asthma was defined as a first diagnosis among those without asthma in the 8 years before cohort entry. Time was classified into pre-pregnancy and each trimester until delivery. We fit inverse probability weighted Poisson models to estimate marginal relative risks (RRs) for prematurity (delivery <37th week), major malformations, and SGA (birth weight <10th percentile) comparing women with and without asthma, assessing the asthma timing of diagnosis interaction term via a Wald test.

Results: In a cohort of 122,880 deliveries, the increased risk of prematurity, but not SGA, due to incident asthma was higher in those diagnosed during the second (RR, 1.34; 95% confidence interval [CI], 1.08-1.65; Wald P = .05) and third (RR, 1.93; 95% CI, 1.62-2.29; Wald P < .01) trimesters relative to pre-pregnancy (RR, 1.06; 95% CI, 0.98-1.15). A trend toward an increased risk of major malformations was observed in those diagnosed during the first trimester (RR, 1.18; 95% CI, 0.94-1.49; Wald P = .15) than pre-pregnancy (RR, 0.99; 95% CI, 0.92-1.07).

Conclusions: Asthma diagnosed during, versus before, pregnancy was associated with a greater prematurity risk, suggesting an important role of preconception and prenatal screening.

Keywords: Asthma diagnosis; Malformations; Perinatal outcomes; Pregnancy; Preterm birth; Small-for-gestational age.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Asthma* / diagnosis
  • Asthma* / epidemiology
  • Cohort Studies
  • Female
  • Humans
  • Infant, Newborn
  • Infant, Small for Gestational Age
  • Pregnancy
  • Pregnancy Complications* / diagnosis
  • Pregnancy Complications* / epidemiology
  • Retrospective Studies