Don't undertreat asthma in pregnancy

August 1, 2005

Doing so can lead to serious—even fatal—complications. To protect mother and fetus alike, manage these patients just as aggressively as your nonpregnant asthmatics.

Could the fear of adverse fetal outcomes from asthma drugs be keeping you from managing pregnant patients with asthma as aggressively as nonpregnant patients? You'll be less tempted to hold back if you keep in mind that nothing is more important to successfully managing a pregnant asthmatic than preventing exacerbations by having her avoid triggers and adhere to her daily medications. And by remembering that asthma drugs pose less risk to the fetus than does a serious asthma attack.

Not only the most common respiratory disease in pregnancy, but also the most common potentially serious medical complication of pregnancy, asthma affects up to 4% of people in general and complicates between 1% and 4% of all pregnancies.1,2 Objective pulmonary testing is crucial to both diagnose and treat asthma during pregnancy.

Asthma, considered an obstructive lung disease, is responsible for 28 million office visits, 1 million emergency room visits, more than 130,000 hospitalizations, and kills roughly 4,000 people in the United States each year.3 Moreover, its incidence in pregnancy appears to be rising.

Although unsubstantiated, the fear of adverse fetal outcomes from asthma drugs has resulted in undertreatment of asthma during pregnancy, leading to serious complications.1-4 This underscores the need to manage a pregnant asthmatic just as aggressively as a non-pregnant patient to minimize the morbidity and mortality to both mother and fetus. Our goal here is to review the definitions, guidelines, and treatment of the pregnant asthmatic.

Classification and pathogenesis Asthma is characterized by reversible airway obstruction, airway inflammation, and increased airway responsiveness to a variety of stimuli. Decreased expiratory flow ensues and the typical clinical syndrome consists of episodic coughing, wheezing, and dyspnea. Atypical symptoms include isolated cough, chest discomfort, or exertional dyspnea.4

How does asthma affect pregnancy? The clinical course of asthma in pregnancy is fairly unpredictable: Roughly one third of pregnant asthmatics experience worsening of symptoms, one third improve, and one third remain the same. Most exacerbations occur between the 24th and 36th weeks of gestation. In contrast, women experience fewer symptoms during weeks 37 to 40 as compared to any other 4-week gestational period. Asthma typically follows a similar clinical course with successive pregnancies-so obviously, if a patient has had a previous pregnancy, the disease's course at that time might provide a clue of what to expect.

The ultimate goal of managing asthma in pregnancy is to prevent hypoxic episodes in the mother and fetus. An exacerbation that causes minor problems for the mother can cause severe complications for the fetus. Because the fetus operates on the steep portion of the oxygen dissociation curve, drops in maternal PaO2-especially below 60 mm Hg-can profoundly reduce fetal PaO2, resulting in fetal hypoxia. Maternal oxygen saturation must remain greater than 95% to assure that the fetus is getting enough oxygen.3-5