Treated and untreated maternal asthma and adverse pregnancy outcomes
Abstract
Background: Continued use of asthma medication during pregnancy is recommended, particularly as asthma exacerbations often increase during pregnancy, and poor control may adversely affect maternal and fetal health. However, evidence on whether adverse outcomes arise from the treatment itself or just the underlying disease remains inconsistent.
Objectives: To examine the relationship between maternal asthma, and its medication, and early pregnancy outcomes.
Study Design: A retrospective birth cohort was constructed using population-wide linked Welsh health records pertaining to 324,238 infants born between 2009 and 2022. Logistic regression was used to investigate associations between maternal asthma (treated, untreated, and medication exposure) and pregnancy outcomes: stillbirth, iatrogenic and spontaneous preterm delivery, small/very small for gestational age (SGA/VSGA), and low Apgar score.
Results: Of the 324,238 infants, 39,040 (12.04%) had mothers with asthma: 20,840 (6.43%) had treated asthma, 8,230 (2.54%) had untreated asthma, and 9,970 (3.07%) received asthma medications without any recorded asthma diagnosis. Treated asthma was associated with SGA (aOR 1.13, 95% CI 1.07-1.19), VSGA (aOR 1.14, 95% CI 1.03-1.26), Apgar score <7 (aOR 1.14, 95% CI 1.01-1.29), and iatrogenic preterm delivery (aOR 1.13, 95% CI 1.01-1.26). Associations were observed across multiple classes of asthma medication, with findings suggesting dose-response relationships. Iatrogenic preterm delivery was also associated with untreated asthma (aOR 1.34, 95% CI 1.13-1.59). No associations were observed with stillbirth.
Conclusions: Observed associations with SGA, VSGA, Apgar score <7 and iatrogenic preterm delivery were likely due to the underlying condition rather than its treatment, with non-specific, dose-dependent associations with medications reflecting confounding by indication and severity. Our findings support guideline recommendations to continue asthma treatment during pregnancy.
Key messages: • This study shows that adverse early pregnancy outcomes are driven by maternal asthma rather than asthma medications, helping resolve uncertainty about the safety of asthma treatments.
• The findings support continuing asthma treatment in pregnancy, helping clinicians avoid undertreatment, reduce exacerbations and protect the fetus from asthma-related adverse effects.
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BibTeX
@article{shakhshir2026treated,
title = {{Treated and untreated maternal asthma and adverse pregnancy outcomes}},
author = {LA Shakhshir and JP Pell and CE Hastie and SM Nelson and S Singh and M Fleming},
journal = {The European Journal of Public Health},
year = {2026},
month = oct,
doi = {10.1093/eurpub/ckag169.220},
url = {https://doi.org/10.1093/eurpub/ckag169.220},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Treated and untreated maternal asthma and adverse pregnancy outcomes
AU - LA Shakhshir
AU - JP Pell
AU - CE Hastie
AU - SM Nelson
AU - S Singh
AU - M Fleming
PY - 2026
DA - 2026/10/01
JO - The European Journal of Public Health
DO - 10.1093/eurpub/ckag169.220
UR - https://doi.org/10.1093/eurpub/ckag169.220
AB - Background: Continued use of asthma medication during pregnancy is recommended, particularly as asthma exacerbations often increase during pregnancy, and poor control may adversely affect maternal and fetal health. However, evidence on whether adverse outcomes arise from the treatment itself or just the underlying disease remains inconsistent. Objectives: To examine the relationship between maternal asthma, and its medication, and early pregnancy outcomes. Study Design: A retrospective birth cohort was constructed using population-wide linked Welsh health records pertaining to 324,238 infants born between 2009 and 2022. Logistic regression was used to investigate associations between maternal asthma (treated, untreated, and medication exposure) and pregnancy outcomes: stillbirth, iatrogenic and spontaneous preterm delivery, small/very small for gestational age (SGA/VSGA), and low Apgar score. Results: Of the 324,238 infants, 39,040 (12.04%) had mothers with asthma: 20,840 (6.43%) had treated asthma, 8,230 (2.54%) had untreated asthma, and 9,970 (3.07%) received asthma medications without any recorded asthma diagnosis. Treated asthma was associated with SGA (aOR 1.13, 95% CI 1.07-1.19), VSGA (aOR 1.14, 95% CI 1.03-1.26), Apgar score <7 (aOR 1.14, 95% CI 1.01-1.29), and iatrogenic preterm delivery (aOR 1.13, 95% CI 1.01-1.26). Associations were observed across multiple classes of asthma medication, with findings suggesting dose-response relationships. Iatrogenic preterm delivery was also associated with untreated asthma (aOR 1.34, 95% CI 1.13-1.59). No associations were observed with stillbirth. Conclusions: Observed associations with SGA, VSGA, Apgar score <7 and iatrogenic preterm delivery were likely due to the underlying condition rather than its treatment, with non-specific, dose-dependent associations with medications reflecting confounding by indication and severity. Our findings support guideline recommendations to continue asthma treatment during pregnancy. Key messages: • This study shows that adverse early pregnancy outcomes are driven by maternal asthma rather than asthma medications, helping resolve uncertainty about the safety of asthma treatments. • The findings support continuing asthma treatment in pregnancy, helping clinicians avoid undertreatment, reduce exacerbations and protect the fetus from asthma-related adverse effects.
SN - 1101-1262
SN - 1464-360X
ER -