Asthma in pregnancy: Clinical sciences

Asthma is an obstructive airway disease characterized by increased airway responsiveness to stimuli, reversible airway obstruction, and chronic airway inflammation. Asthma has a variable course in pregnancy with about a third of patients experiencing improvement in their symptoms, a third having worsening of their symptoms, and a third whose symptoms remain the same. It’s classified as mild, intermittent, or severe and requires close surveillance to ensure adequate oxygenation of the fetus by preventing hypoxic episodes in the patient. Those with mild and well-controlled moderate asthma tend to do well and have excellent pregnancy outcomes.

However, those with severe and poorly controlled asthma may have an increased risk of perinatal complications like preeclampsia, fetal growth restriction, and premature birth. Additionally, severe asthma exacerbations may cause life-threatening respiratory failure. When counseling patients on treatment options it’s important to use a stepwise approach to medical intervention based on their asthma classification and emphasize that a healthy fetus first requires a healthy patient!

If a patient presents with a chief concern suggesting asthma in pregnancy you should first perform an ABCDE assessment to determine if the patient is stable or unstable. In unstable patients, the first step involves acute management to stabilize the airway, breathing, and circulation. Then, obtain IV access and monitor maternal vital signs. Also, be sure to assess fetal well-being, depending on the gestational age. If the pregnancy is previable, obtain fetal heart tones via Doppler. In pregnancies past 22 weeks, perform continuous electronic fetal monitoring and consider a biophysical profile. Finally, if a patient has severe asthma symptoms, including drowsiness, confusion, or an elevated partial pressure of carbon dioxide or PCO2, consider hospitalization with admission to the intensive care unit.

Now that unstable patients are taken care of, let’s talk about stable patients. Start by performing a focused history and physical, as well as spirometry, or pulmonary function testing. Patients may report dyspnea, cough, or chest tightness, as well as a known history of asthma. Often symptoms will be worse at night and might be triggered by allergens, infection, or exercise. On physical exam, you will likely note wheezing or tachypnea. Finally, spirometry might reveal reversible airway obstruction.

Here’s a clinical pearl! Pulmonary function testing is performed with a handheld spirometer. When performing, instruct your patient to take a maximal breath in, then forcibly exhale all of the air from their lungs into the spirometer. A flow-volume loop is then generated, which differentiates between obstructive and restrictive lung disease.

Before moving on to treatment, you need to assess the severity of your patient's symptoms. The four components to take into account include your patient’s symptom frequency per week, number of nighttime awakenings, whether their asthma causes interference with normal activities, and their forced expiratory volume in 1 second, or FEV1 as noted on a peak flow meter. Also be sure to review any prior asthma-related hospitalizations including ICU admissions, intubations, and emergency room visits; as well as any requirement of unscheduled treatments, including oral corticosteroids. If a patient has been treated during a prior pregnancy, be sure to ask about how their asthma was managed, as this may predict a future response.

Okay, let’s look at our first category. Now, if your patient reports having symptoms no more than 2 days per week, nighttime awakenings no more than twice per month, no interference with normal activities, and their FEV1 or peak flow is greater than 80 percent you can diagnose mild intermittent asthma. These patients do not require daily medication and can be treated with albuterol as needed for episodic symptom management. Continue to reassess your patient throughout pregnancy as their severity may change which would require adjusting their medications.