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Overview

Asthma is the most common potentially serious medical condition to complicate pregnancy. In fact, asthma affects approximately 8 percent of women in their childbearing years. Well-controlled asthma is not associated with significant risk to mother or fetus. Uncontrolled asthma can cause serious complications to the mother, including high blood pressure, toxemia, premature delivery and rarely death. For the baby, complications of uncontrolled asthma include increased risk of stillbirth, fetal growth retardation, premature birth, low birth weight and a low APGAR score at birth.

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Asthma can be controlled by careful medical management and avoidance of known triggers, so asthma need not be a reason for avoiding pregnancy. Most measures used to control asthma are not harmful to the developing fetus and do not appear to contribute to either miscarriage or birth defects.

Although the outcome of any pregnancy can never be guaranteed, most women with asthma and allergies do well with proper medical management by physicians familiar with these disorders and the changes that occur during pregnancy.

Symptoms

Asthma is a condition characterized by obstruction in the airways of the lungs caused by spasm of surrounding muscles, accumulation of mucus, and swelling of the airway walls due to the gathering of inflammatory cells. Unlike individuals with emphysema who have irreversible destruction of their lung cells, asthmatic patients usually have a condition that can be reversed with vigorous treatment.

Individuals with asthma most often describe what they feel in their airways as a "tightness." They also describe wheezing, shortness of breath, chest pain and cough. Symptoms of asthma can be triggered by allergens (including pollen, mold, animals, feathers, house dust mites and cockroaches), other environmental factors, exercise, infections and stress.

Effects of Pregnancy on Asthma

When women with asthma become pregnant, one-third of the patients improve, one-third worsen, and the last third remain unchanged. Although studies vary widely on the overall effect of pregnancy on asthma, several reviews find the following similar trends:

  • Women with severe asthma are more likely to worsen, while those with mild asthma are more likely to improve or remain unchanged.
  • The change in the course of asthma in an individual woman during pregnancy tends to be similar on successive pregnancies.
  • Asthma exacerbations are most likely to appear during the weeks 24 to 36 of gestation, with only occasional patients (10 percent or fewer) becoming symptomatic during labor and delivery.
  • The changes in asthma noted during pregnancy usually return to pre-pregnancy status within three months of delivery.

Pregnancy may affect asthmatic patients in several ways. Hormonal changes that occur during pregnancy may affect both the nose and sinuses, as well as the lungs. An increase in the hormone estrogen contributes to congestion of the capillaries (tiny blood vessels) in the lining of the nose, which in turn leads to a "stuffy" nose in pregnancy (especially during the third trimester). A rise in progesterone causes increased respiratory drive, and a feeling of shortness of breath may be experienced as a result of this hormonal increase. These events may be confused with or add to allergic or other triggers of asthma. Spirometry and peak flow are measurements of airflow obstruction (a marker of asthma) that help your physician determine if asthma is the cause of shortness of breath during pregnancy.

Asthma is a disease in which intensity of symptoms can vary from day to day, month to month, or season to season regardless of pregnancy. Therefore, a treatment plan should be chosen based both on asthma severity and experience during pregnancy with those medications. Remember that the use of medications should not replace avoidance of allergens or irritants, as avoidance will potentially reduce medication needs.

In general, asthma medications used in pregnancy are chosen based on the following criteria:

  • Inhaled medications are generally preferred because they have a more localized effect with only small amounts entering the bloodstream.
  • When appropriate, time-tested older medications are preferred since there is more experience with their use during pregnancy.
  • Medication use is limited in the first trimester as much as possible when the fetus is forming. Birth defects from medications are rare (no more than 1 percent of all birth defects are attributable to all medications.
  • In general, the same medications used during pregnancy are appropriate during labor and delivery and when nursing.

Management and Treatment

Bronchodilator medication

Short-acting inhaled beta2-agonists, often called "asthma relievers" or "rescue medications," are used as necessary to control acute symptoms. Albuterol is the preferred short-acting inhaled beta2-agonist for use during pregnancy since there are more available reassuring human gestational safety data.

Two long-acting inhaled beta agonist, salmeterol (Serevent®) and formoterol (Foradil®), are available. No large-scale trials of these medications in pregnancy have been performed. However, because of their inhaled route, chemical relation to albuterol, and efficacy data, long-acting beta agonists are recommended during pregnancy for patients not controlled on inhaled corticosteroids.

Theophylline has extensive human experience without evidence of significant abnormalities. Newborns can have jitteriness, vomiting and fast pulse if the maternal blood level is too high. Therefore, patients who receive theophylline should have blood levels checked during pregnancy.

Ipratropium (Atrovent®), an anticholinergic bronchodilator medication, does not cause problems in animals; however, there is no published experience in humans. Ipratropium is absorbed less than similar medications in this class, such as atropine.

Anti-inflammatory medication

The anti-inflammatory medications are preventive, or "asthma controllers," and include inhaled cromolyn (Intal®), corticosteroids and leukotriene modifiers. Patients requiring the use of beta2-agonists more often than three times a week, or who have reduced peak flow readings or spirometry (lung function studies), usually need daily anti-inflammatory medication. Inhaled cromolyn sodium is virtually devoid of side effects but is less effective than inhaled corticosteroids.

Budesonide (Pulmicort®) is recommended as the inhaled corticosteroid of choice for use during pregnancy due to a large amount of reassuring human gestational safety data. However, other inhaled corticosteroids (such as beclomethasone [Qvar®], fluticasone [Flovent®], flunisolide [Aerobid®], mometasome [Asmanex®], and triamcinolone [Azmacort®] have not been proven to be unsafe during pregnancy and can be continued in patients well-controlled by them prior to pregnancy.

In some cases oral or injectable corticosteroids, such as prednisone, prednisolone or methyprednisolone may be necessary for a few days in patients with severe asthma exacerbations or throughout pregnancy in women with severe asthma. . Some studies have demonstrated a slight increase in the incidence of pre-eclampsia, premature deliveries or low-birth-weight infants with chronic use of corticosteroids. However, they are the most effective drugs for the treatment of patients with more severe asthma and other allergic disorders. Therefore, their significant benefit usually far exceeds their minimal risk.

Three leukotriene modifiers, montelukast (Singulair®), zafirlukast (Accolate®), and zileuton (Zyflo®) are available. Results of animal studies are reassuring for montelukast and zafirlukast , but there are minimal data in human pregnancy with this new class of anti-inflammatory drugs.

Fetal monitoring

For pregnant women with asthma, the type and frequency of fetal evaluation is based on gestational age and maternal risk factors. Ultrasound can be performed before 12 weeks if there is concern about the accuracy of an estimated due date and repeated later if a slowing of fetal growth is suspected. Electronic heart rate monitoring, called "non-stress testing" or "contraction stress testing," and ultrasonic determinations in the third trimester may be used to assess fetal well being. For third trimester patients with significant asthma symptoms, the frequency of fetal assessment should be increased if problems are suspected. Asthma patients should record fetal activity or kick counts daily to help monitor their baby according to their physician's instructions.

During a severe asthma attack in which symptoms do not quickly improve, there is risk for significant maternal hypoxemia, a low oxygen state. This is an important time for fetal assessment; continuous electronic fetal heart rate monitoring may be necessary along with measurements of the mother's lung function.

Fortunately during labor and delivery, the majority of asthma patients do well, although careful fetal monitoring remains very important. In low risk patients whose asthma is well-controlled, fetal assessment can be accomplished by 20 minutes of electronic monitoring (the admission test). Intensive fetal monitoring with careful observation is recommended for patients who enter labor and delivery with severe asthma, have a non-reassuring admission test, or other risk factors.

FAQs

Can any of the medications I take for my asthma cause harm to my baby?

Most medications used to treat asthma appear to be safe, especially those that have been around for many years and have been time tested. Unfortunately, it is very difficult to do adequate studies in pregnant women to prove the safety of drugs.
Since we cannot prove the safety of drugs taken during pregnancy, should I stop taking my asthma medication as soon as I discover that I have become pregnant?

No. A moderate to severe asthma attack should be a risk to both you and the baby. The risks of stopping your medication are far greater than any potential risk to your baby. Therefore, do not stop your regular asthma medication unless your doctor recommends it.

Are other medications taken for my hay fever or other allergies also safe?

Probably. However, some minor birth defects have been linked to certain antihistamines and decongestants in some studies, but study results have not been consistent. It would be best to call your physician before continuing antihistamines or decongestants, even those available over the counter.

If I become short of breath, how can my doctor know if my baby is getting sufficient oxygen?

There are tests that can accurately assess the breathing status of the mother, such as spirometry, arterial blood gases or pulse oximetry. Spirometry, an office breathing test, measures air flow into the lungs. A blood gas study is done in the hospital to measure oxygen content of the blood. Pulse oximetry is a way of estimating the oxygen content of the blood without a needle stick. Results on all three tests are available almost immediately.

Are there any medications that should be avoided during pregnancy?

Unless a life-threatening illness dictates their need, the following medications should be avoided during pregnancy either entirely or during early or later stages:

  • Sulfonamides (the "sulfa" drugs) are safe early in pregnancy, but their use in the last trimester might result in a jaundiced infant;
  • Tetracyclines may cause skeletal and dental deformities;

Will asthma have any effect on my pregnancy and on the baby?

If uncontrolled, severe asthma may be harmful to the developing fetus. However, if well-controlled, it should not have adverse effect on you or your baby.

How does severe, uncontrolled asthma adversely affect the fetus?

The developing fetus depends on the mother to supply oxygen for growth and survival. Oxygen dissolved in her blood is transferred through the placenta to the fetus. Uncontrolled asthma causes a decrease in the mother's oxygen which, in turn, reduces the oxygen available to the developing fetus. This may result in impaired fetal growth; it could even affect survival of the fetus.

Will my asthma worsen during pregnancy? Is there any greater risk during labor and delivery?

Your asthma may worsen, stay unchanged or possibly improve during pregnancy. Although it cannot be accurately predicted in a first pregnancy, asthma usually follows the same course in subsequent pregnancies. For reasons not totally understood, asthma usually improves during labor and delivery, but even if a severe attack occurs then, appropriate treatment can be given, and complications are rare.

Can asthma medications safely be used during pregnancy?

Though no medication has been proven entirely safe for use during pregnancy, your doctor will carefully balance medication use and symptom control. Your treatment plan will be individualized so that potential benefits of medications outweigh the potential risks of these medications or of uncontrolled asthma.