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Asthma is a maternal medical condition that can have a profound impact on pregnancy. The incidence of asthma in pregnancy makes it a common comorbidity that a practitioner will encounter and the most common respiratory disorder found in pregnancy. Asthma affects approximately 4% to 8% of pregnant women and the prevalence seems to be increasing.1 The range of severity and high prevalence of the condition can make it an overlooked part of the medical history, even though it can become a life-threatening condition.

The general rule for asthma in pregnancy has been that one-third will improve, one-third will worsen, and one-third will remain stable. A recent study has disproven the latter. Instead, two factors significantly impact the course of the disease throughout pregnancy: pre-pregnancy severity, specifically in the 1 year before pregnancy, and adherence to medications prescribed according to Global Initiative for Asthma guidelines. Patients who discontinue or are noncompliant with therapy will be more likely to worsen, even if their initial classification is less severe.2


The initial history of asthma should be elicited before conception or at the first prenatal visit. For those who do not carry a diagnosis of asthma, certain components of the history and physical exam can lead to a clinical suspicion for undiagnosed asthma. History of a chronic cough, which is typically worse at night, wheezing, chest tightness, or difficulty breathing, can be initial symptoms. Exercise, viral infections, pets, dust, smoke, and other irritants that trigger or worsen symptoms should prompt a provider to consider a diagnosis of asthma. Wheezing heard on lung exam is a common sign, although is not necessary for the diagnosis. Any of these findings can heighten clinical suspicion and a provider can consider obtaining pulmonary function testing to establish the diagnosis.3

Asthma exacerbations typically present with an acute worsening of respiratory symptoms, including cough, wheezing, chest tightness, and dyspnea. A 20% decrease in peak expiratory flow (PEF) may be seen on spirometry. A subjective decrease in fetal movement can be an early symptom of an asthma exacerbation.4 Asthma exacerbations are more common in noncompliant patients or patients with persistent asthma. One study found that exacerbations requiring medical intervention occurred in almost 5% of pregnancies complicated by asthma, although other studies have estimated as many as 36% of patients had exacerbations.5 Exacerbations were more common in women who had more severe asthma. This study did not find that any trimester was associated with an increased risk for exacerbation.5


Asthma is a chronic respiratory condition because of interactions of inflammation, airflow obstruction, and bronchial hyperresponsiveness. Allergens and respiratory infections are important contributors to the development and persistence of asthma. Asthma is clinically diagnosed by the presence of intermittent airflow obstruction or airway hyperresponsiveness that is at least partially reversible, while excluding other causes.3 The ...

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