Asthma control during pregnancy: revisiting better/same/worse

Published: October 14, 2021

Asthma affects 10% of pregnancies, and decreased asthma control during pregnancy has been associated with poor pregnancy outcomes. However, the course of asthma during pregnancy is not well understood. Convention holds that asthma follows a rule of thirds during pregnancy: a third experience increased control (get better), a third experience no change in control (stay the same), and the rest experience decreased control (get worse). This “better, same, worse” convention has predominated in the asthma literature since the 1990’s, despite a lack of studies prospectively and agnostically examining asthma control during pregnancy. This study aimed to use data-driven methods to better understand the course of asthma during pregnancy.

In an original article in The Journal of Allergy and Clinical Immunology: In Practice, Stevens et al. examined asthma control across pregnancy in the Breathe - Wellbeing, Environment, Lifestyle, and Lung function (B-WELL-Mom) Cohort, a prospective pregnancy cohort of women with and without asthma. Patterns of asthma control across pregnancy were identified from daily diary records of activity limitation, nighttime symptoms, inhaler use, and respiratory symptoms using a machine learning algorithm. The authors then explored whether these patterns of asthma control could be attributed to pregnancy alone and examined sociodemographic and clinical characteristics associated with experiencing a given pattern of asthma control.

Contrary to the “better, same, worse” convention, the authors identified only 2 patterns of asthma control during pregnancy – same and worse. In the first (“same”), 40% of asthmatic pregnant women experienced infrequent and stable activity limitation, inhaler use, and respiratory symptoms, as well as infrequent and slightly increasing nighttime symptoms. In the second (“worse”), 60% of women experienced frequent and stable activity limitation and inhaler use, as well as frequent and increasing nighttime and respiratory symptoms. Examination of symptoms reported by women without asthma (activity limitation, etc.) suggested that pregnancy alone was not responsible for changes over time, and that asthma-specific mechanisms may be at play. Several sociodemographic and clinical characteristics – including poorer pre-pregnancy asthma control – were associated with worse asthma control during pregnancy. These at-risk patients may require closer symptom monitoring as well as additional counselling in trigger identification and avoidance during pregnancy.  

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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