TOPLINE:

The use of inhaled corticosteroids (ICS) during pregnancy may diminish the association between maternal asthma and reduced infant lung function and thus may improve respiratory health in infants born to mothers with asthma.

METHODOLOGY:

• Researchers assessed lung function in infants aged 4-6 weeks from two prospective birth cohorts — one involving pregnant women with asthma (May 2014 to December 2019 ) and the other without asthma (November 2021 to September 2023 ) — to evaluate the effect of ICS use during pregnancy on infant lung function.
• Infant lung function was measured using tidal breathing flow volume loops and functional residual capacity.
• They also used parameters — including the ratio of time to peak tidal expiratory flow to expiratory time ( tPTEF:tE) normalized to functional residual capacity — to provide a more comparable, sensitive measure of airway function in infants by accounting for differences in lung size and development.
• The outcome was compared across 232 infants: those born to mothers with asthma who used ICS during pregnancy (n = 161; 49.7% boys), those born to mothers with asthma who did not use ICS (n = 25; 60% boys), and those born to mothers without asthma (reference group; n = 46; 65.2% boys).
• Maternal use of ICS during pregnancy was defined as either a positive report of use at any prenatal visit or a retrospective report of use at the postpartum interview.

TAKEAWAY:

• Among infants born to mothers with asthma, those exposed to ICS during pregnancy vs those not exposed to ICS had a significant increase in tPTEF:tE to functional residual capacity ratio (coefficient, 0.06; P = .014).
• Compared with the reference group, infants of mothers with asthma who did not use ICS had a statistically significant lower tPTEF:tE to functional residual capacity ratio (coefficient, -0.08; P = .012), whereas no significant difference was observed in infants whose mothers used ICS.
• Only boys showed a significant trend toward improvement in tPTEF:tE corrected for functional residual capacity (trend coefficient, -0.04; P = .013).

IN PRACTICE:

“Notably, there were no significant differences between infants born to mothers without asthma versus those born to mothers with asthma who used ICS during pregnancy for tPTEF:tE corrected for FRC [functional residual capacity]. This suggests that ICS use may improve aspects of infant lung function to a level that is observed in infants born to mothers without asthma,” the authors wrote.

SOURCE:

This study was led by Gabriela Martins Costa Gomes, Hunter Medical Research Institute, The University of Newcastle, Newcastle, Australia. It was published online on November 9, 2025, in Thorax.

LIMITATIONS:

As the cohorts were recruited in different periods they may have had differential exposure to environmental factors such as circulation of respiratory syncytial virus. Maternal use of ICS was ascertained by prospective or retrospective self ‑ report, which may have introduced reporting bias, and the study lacked information on ICS timing, dose, and cumulative exposure.

DISCLOSURES:

This study was supported by the National Health and Medical Research Council, the Hunter Medical Research Institute, and the Hunter Children’s Research Foundation. One author reported receiving grant funding from the Australian Medical Research Future Fund.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.