1996 OPEN FORUM Abstracts
Women's Issues in Asthma
Sue A. Ravenscraft, MD Tuesday, November 5, 1996
During pregnancy approximately 1/3 of women will experience more difficulty controlling their disease and 1/3 of women will actually improve. Patients with severe preexisting asthma tend to worsen. Progesterone induced hyperventilation ("dyspnea of pregnancy") is present even in the first trimester and minute ventilation increases by close to 50% at term (PaCO2 = 30-32 mmHg). This increase in minute ventilation is due to an increase in tidal volume; respiratory rate is relatively unchanged. Changes in pulmonary function at term include a decrease in residual volume, a small decrement in total lung capacity, and an increase in inspiratory capacity. FEV1 does not change and can be followed throughout pregnancy. Uncontrolled asthma during pregnancy can produce serious maternal and fetal complications. Maternal complications include preeclampsia, gestational hypertension, hyperemesis gravidarum, toxemia, and induced or complicated labors. Fetal complications include increased risk of perinatal mortality, intrauterine growth retardation, preterm birth, and low birth weight. When asthma is properly controlled, however, pregnant women can maintain a normal pregnancy with little risk to themselves or their fetuses. Asthma must be treated as aggressively in pregnant women as it is in nonpregnant women. Underestimation of asthma severity and undertreatment of exacerbations are two common errors that may lead to adverse maternal and fetal outcomes. Early (12-20 week) fetal monitoring with sonography provides a benchmark for progressive fetal growth. Sequential sonographic evaluations are indicated in second and third trimesters if asthma is moderate or severe or if growth retardation is suspected. Patients with anything more than mild occasional asthma should be treated with anti-inflammatory agents (inhaled steroids or cromolyn). Theophylline can be added as needed but lower blood levels should be maintained. When coming in with active labor, patients who have required chronic systemic corticosteroids during pregnancy should be given hydrocortisone to treat possible adrenal suppression. Medications to avoid during pregnancy include alpha-adrenergic compounds (other than pseudoephedrine), iodides, sulfonamides (late pregnancy), tetracycline, and quinalones. Approximately 10% of women will exacerbate during labor. During labor induction and treatment of postpartum hemorrhage oxytocin is the drug of choice. Methylergonovine and ergonovine should be avoided if possible since may cause bronchospasm.