Asthma is probably the most common potentially serious medical complication during pregnancy.(49) Four percent of all gravidas have a history of asthma, and up to 10% of the population have nonspecific airway hyperresponsiveness.(34) Although the etiology is uncertain, the prevalence of asthma has been increasing (by 60% from 1980 to 1989); hospitalizations and mortality secondary to asthma exacerbations have also increased.(34) The management of asthma during pregnancy is complicated because the efficacy of the common medical therapies has not been well studied during pregnancy, and medications may have untoward fetal and maternal effects. Suboptimal control resulting in maternal exacerbations can cause serious fetal sequelae. In general, pregnancy does not appear to affect markedly the severity or control of asthma.(34) However, asthma is associated with considerable maternal morbidity. Mabie et al(33) reported that 42.5% of their patients required hospitalization, and an additional 18% had one or more emergency room visits for asthma exacerbations during pregnancy. Perlow et al(40) reported a 46% rate of hospital admissions for their gravid asthmatics. Pregnant women with asthma have also been shown to have an increased risk of preeclampsia and delivery by cesarean section.(30, 48, 54) Asthma is associated with an increased incidence of perinatal mortality, prematurity, low birth weight, and neonatal hypoxia.(4, 22, 30) Several studies have failed to confirm some or all of these previous observations.(10, 30, 33, 48, 54) Although birth weight has been commonly used as an outcome measure, few studies controlled for confounding factors known to affect birth weight, such as maternal race, height, weight, parity, nutrition, chronic hypertension, and cigarette smoking. Asthmatics have increased frequencies of chronic hypertension and maternal smoking, which may confound the effects of other influences.(10, 48, 50) In a large prospective study lasting 12 years, Schatz and colleagues(50) compared 486 pairs of pregnant asthmatics and pregnant nonasthmatic controls matched for age, parity, smoking, and year of delivery. There were no significant differences in the incidences of preeclampsia, perinatal mortality, congenital malformations, or low birth weight between the two groups. Ethnicity may be a particularly important factor, because African-Americans (ages 15 to 44) are five times more likely to die from asthma and are twice as likely to be hospitalized for asthma as European-Americans.(35) Poor control of asthma leading to chronic or episodic fetal hypoxia is thought to be an important cause of perinatal morbidity and mortality. Most medications used in treating asthma appear to have minimal or no effects on the fetus. However, steroids may be associated with low birth weight and preeclampsia.(34) In 1993, the National Asthma Education Program (NAEP) published the working group's report ''Management of Asthma During Pregnancy.''(34) This report included an overview of the pathogenesis, diagnosis, management, and classification of asthma according to symptomatic and objective criteria. Mild asthma includes brief (< 1 hour) symptomatic exacerbations (wheezing, cough, and/or dyspnea) up to two times weekly. The peak expiratory flow rate (PEFR) and forced expiration in one second (FEV1) are greater than or equal to 80% of predicted. Moderate asthma is characterized as having symptomatic exacerbations more than twice a week, with PEFR and FEV, ranging from 60% to 80% of that predicted. Severe asthma includes continuous symptoms with frequent exacerbations that limit activity levels. Pulmonary functions are < 60% of expected and are highly variable. Women with more severe asthma may have the greatest risk for complications during pregnancy.(20, 40) The NAEP working group report stressed that effective management of asthma during pregnancy relies on four integral components: (1) objective measurements of maternal lung function and fetal well being, (2) patient education, (3) avoiding or controlling asthma triggers, and (4) pharmacologic therapy.
