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Allied Health: Articles of Interest Managing asthma during pregnancy minimizes risk of complications Asthma is a chronic disease that complicates up to 7 percent of pregnancies. Because uncontrolled asthma may increase the risk of perinatal maternal and fetal complications, asthma therapy may be necessary. In deciding how to manage pregnant asthmatics, some questions must be considered:
The effects of pregnancy in asthmatic women are described by the rule of thirds: one third of asthmatics improve with pregnancy, one third worsen, and one third remain unchanged. Despite this, patients with severe asthma prior to pregnancy are more likely to worsen during pregnancy and subsequent pregnancies tend to follow a similar course as the first pregnancy in any given patient. In addition, asthma exacerbations occur most frequently in the second trimester. Overall, asthma may be improved by some normal chemical variations of pregnancy (i.e. increased progesterone) and worsened by others (i.e. decreased functional residual capacity). Depending on the individual, this results in improved, stable, or worsened asthma. Uncontrolled asthma, may increase the risk of low birth weight (LBW) infants, pre-term births, perinatal mortality, maternal hypertension, pre-eclampsia, placenta previa, uterine hemorrhage, and Caesarian delivery. Adverse perinatal outcomes in poorly controlled asthmatic women include hypoxia and reduced uteroplacental blood flow due to hypocapnea, alkalosis, dehydration, and hypertension. Asthma medications and other factors (i.e. infection) may also play a role. Severe asthma during pregnancy has been associated with maternal and fetal deaths. Asthmatic women hospitalized for asthma during pregnancy are more likely to have LBW infants than those who did not require emergency therapy. In fact, maternal FEV1 corresponds with ponderal indices of the infant. To avoid adverse outcomes in pregnant asthmatics and their babies, controller and rescue medications may be necessary. When choosing medications, things to consider include:
The current FDA pregnancy categories are shown in Figure 1.
Asthma medications are divided into two types. Rescue medications include short-acting beta-agonists, anticholinergics, and systemic corticosteroids. Cromolyn, nedocromil, inhaled corticosteroids, leukotriene modifiers, long-acting beta-agonists, and theophylline are all used as preventive or controller therapies. Short-acting beta-agonists induce bronchodilation and are the initial rescue therapy in pregnant and non-pregnant asthmatics. Although this class of medications has a pregnancy category C rating, the human data for albuterol, metaproterenol, and terbutaline is reassuring. Anticholinergics (category B), also bronchodilators, are usually added to short-acting beta-agonists for additional rescue therapy. Corticosteroids (category C) are used for asthma exacerbations that do not respond to initial rescue therapies. Unfortunately, their use in pregnancy is associated with a 3-6 fold increased risk of oral clefts and LBW in infants, as well as maternal pre-eclampsia. However, when indicated for management of severe asthma, these risks of therapy are much less than the risks of uncontrolled severe asthma that can include maternal and/or fetal death. To avoid both uncontrolled asthma in the mother and minimize the use of corticosteroids, preventive therapy with controller medications is paramount. The choice of controller therapy may differ in the pregnant versus the non-pregnant asthmatic. The first therapy currently recommended by the ACAAI-ACOG 2000 position paper is still cromolyn or nedocromil (category B) because of reassuring animal and human data for use during pregnancy. Unfortunately, these are most efficacious in mild asthmatics and further therapy is usually warranted. Inhaled corticosteroids are the most effective prophylactic therapy for asthma and both beclomethasone and budesonide have reassuring human data during pregnancy. In fact, the FDA changed budesonide from pregnancy category C to B (all other inhaled corticosteroids are C). The ACAAI-ACOG 2000 position paper recommends the addition of salmeterol (a long-acting beta-agonist) only in patients not controlled by a maximum dose of inhaled corticosteroids. Leukotriene modifiers (montelukast and zafirlukast, both category B) have been used in the therapy of asthma. However, no human data is available and as a systemic medication, it should be used in pregnancy only if it was effective for the patient prior to pregnancy. Theophylline (category C) has reassuring human data and may be considered in patients not controlled by inhaled corticosteroids. Another category of therapy important to consider in pregnant asthmatics are vaccines. Because a high percentage of asthmatics also suffer from allergies, they may be on immunotherapy. There are no adverse effects on pregnancy outcomes from immunotherapy, but because anaphylaxis poses a risk for both mother and baby there are specific recommendations for administering it during pregnancy. These include: 1) carefully continue ongoing effective immunotherapy in patients without systemic reactions, 2) do not commence immunotherapy during pregnancy, and 3) do not increase the strength of allergen extract during pregnancy. It is also important that pregnant women with high-risk conditions (chronic heart, lung, or kidney disease, asthma, diabetes, anemia, or immunosuppression) be immunized with the influenza vaccine regardless of their stage of pregnancy. Management of the pregnant woman with persistent asthma should include monthly visits to allow: 1) discussion of symptoms and review of an asthma action plan, 2) lung auscultation, 3) spirometry, and 4) communication between the patient, her obstetrician, and her asthma specialist. When the patient has labor and delivery, prophylactic medications should be continued and patients with frequent corticosteriod use during the pregnancy should receive stress doses of intravenous corticosteroids. It is rare that acute asthma exacerbations occur during labor and delivery, but if they happen at any time during pregnancy it should be managed similar to the non-pregnant patient. Oxygen, fluids and fetal assessment should accompany inhaled beta-agonists, anticholinergics, and intravenous methylprednisolone. Terbutaline, magnesium sulfate, and aminophylline may also be necessary. In conclusion, asthma may change course during pregnancy and maternal asthma may increase the risks of adverse perinatal outcomes. Appropriate management of asthma during pregnancy by both the obstetrician and an asthma specialist should minimize these risks and optimize the health of both the mother and the baby. I would like to thank Dr. Michael Schatz whose excellent research and numerous articles in the area of asthma and pregnancy inspired my own interest in this topic. More detailed information on this topic may be found in his review of asthma and pregnancy in the Annals of Allergy, Asthma, and Immunology, May 2000. |
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