Asthma and Pregnancy

Asthma complicates from 4 to 6 percent of all pregnancies and is considered one of the common problems that may occur during pregnancy. It may also be a serious complication of pregnancy that affects both mother and child.

Rationale for Treatment

Treating asthma during pregnancy varies little from the general treatment of bronchial asthma. The basis of this principle is that the developing fetus depends on the maternal circulation for its supply of oxygen. If the mother suffers uncontrolled asthma, oxygen levels are reduced, creating a threat to the unborn child. Therefore, the medications for treating asthma are usually maintained during pregnancy. Any medication judged unnecessary or which is unsafe during pregnancy should be withdrawn.

Complications of Unstable Asthma and Pregnancy

Studies have shown that pregnant women with uncontrolled, unstable asthma have complicated pregnancies. These complications include premature birth, increased perinatal mortality, and low birth weight. Pregnant women with severe asthma may suffer from high blood pressure, vaginal hemorrhage, and toxemia, and have induced or complicated labor.

Fetal Monitoring

Once pregnancy is confirmed, a patient's obstetrician and the physician responsible for the treatment of the patient's asthma should confer. In view of the potential for complications during pregnancy, fetal monitoring will be stressed. In women with moderate or severe asthma this monitoring will include early ultrasonography (at twelve to twenty weeks). In these patients and those who have had frequent asthma attacks during pregnancy, this procedure and monitoring of the fetal heart rate will be repeated frequently during the third trimester.

Diagnosing Asthma during Pregnancy

Asthma may occur for the first time during pregnancy. The diagnosis may be obscured because shortness of breath is common in pregnancy. Increased progesterone levels in pregnancy seem to stimulate respiration, resulting in hyperventilation and shortness of breath. This may occur early in pregnancy. In the later stages of pregnancy shortness of breath is also common due to enlargement of the uterus limiting full inspiration. Asthma may still be diagnosed correctly, however, with a thorough history and physical exam combined with spirometry. Flow rate measurements remain accurate in pregnancy even in the third trimester when lung volumes may be reduced by enlargement of the uterus. Oxygen measurements are particularly useful in monitoring asthma during pregnancy. This may be done easily with the pulse oximeter. Any significant decrease in oxygen levels must be closely followed and reversed through aggressive treatment.

Course of Asthma during Pregnancy

The course of asthma during pregnancy has been the subject of study. Just as the disease varies from patient to patient, the severity of asthma during pregnancy will also vary. Approximately a third of patients will suffer worsening of their symptoms while the rest will improve or stay the same. This course also appears to be consistent for subsequent pregnancies. If asthma worsens it often happens between twenty four and thirty-six weeks of the pregnancy with subsequent improvement. Exacerbations during labor and delivery are rare. Approximately three months postpartum patients will usually return to the degree of asthma they were experiencing prior to pregnancy.

Asthma Medications during Pregnancy

The general principles of maintaining good control of bronchial asthma should be vigorously applied throughout a patient's pregnancy. Patients should maintain their environmental control precautions and avoid as many allergens as possible. Peak flows should be recorded daily and medications maintained and adjusted accordingly. Understandably, there is a natural reluctance to take medications during pregnancy. In general, asthma medications have been found to be safe during pregnancy and should be continued under the guidance of the physician in consultation with the patient's obstetrician.

General Guidelines: Preferred Medications

The data on the effects of the asthma drugs during pregnancy comes from both human and animal studies. The results of animal studies should be reviewed with the knowledge that effects noted in animals may not apply to humans. Some general guidelines for use of asthma drugs can be applied. Inhaled medications are preferred since these agents do not have as much total body effect as oral or injectable agents. As a rule, medications that have been in use longer are also preferred since there is greater experience with their use.

Which Drugs Are Preferred during Pregnancy?

Bronchodilators

B2-AGONISTS The inhaled B2-agonists (albuterol, metaproterenol, pirbuterol, terbutaline) are the first-line bronchodilators for as needed use during pregnancy. As a group, there is extensive human experience with no evidence of fetal injury. Animal studies are also generally without evidence for adverse effects except at high doses. Terbutaline is often preferred due to negative animal studies. When given by inhalation in normal dosages, all the above agents may be used safely throughout pregnancy, labor, and delivery. The B2-agonists may also be used orally and by nebulization if deemed necessary. If a B-agonist is given by mouth, terbutaline is considered the preferred oral agent. In patients with mild asthma (no more than two attacks a week; no nocturnal attacks), the B2-agonists may be adequate for controlling the patient's bronchial asthma during pregnancy.

Avoid Nonselective Agents Nonselective B-agonists are best avoided during pregnancy. These agents, such as epinephrine (adrenaline) and isoproterenol have both beta-1 and beta-2 effects. Animal studies of these agents have demonstrated abnormal embryo development. Reports from human studies have raised questions concerning their safety. In view of the fact that the selective B2-agonists are available, there is no need to utilize the nonselective medications.

Theophylline Theophylline may also be used as a bronchodilator in pregnancy. There is extensive favorable human experience with this agent. Theophylline may be used intravenously as aminophylline in an emergency. It is essential that blood levels be monitored closely during pregnancy. It is recommended that theophylline levels should not be greater than 12 mg/L, since infants born of women with higher levels have been found to have adverse effects of theophylline such as jitteriness, vomiting, and rapid heartbeat.

Anticholinergic Agents The anticholinergic agent ipratropium bromide has not been studied in humans during pregnancy. Animal studies, however, have not shown any evidence of abnormal fetal development. Since this agent is a relatively weak bronchodilator in asthmatic patients, it should not be considered a preferred agent during pregnancy.

Anti-Inflammatory Agents

Cromolyn Sodium Cromolyn sodium is a nonsteroidal anti-inflammatory agent that may be used safely during pregnancy. Both human and animal studies have had favorable results. In view of the extremely low incidence of adverse effects of cromolyn sodium, it should be regarded as the preferred anti-inflammatory agent in pregnancy. In patients for whom cromolyn is not effective, the inhaled corticosteroids should be introduced. Both agents may be given in patients with severe bronchial asthma.

Inhaled Corticosteroids: Beclomethasone Anti-inflammatory agents are also needed during pregnancy for patients with more than mild asthma. Inhaled corticosteroids are effective agents that can be used safely during pregnancy. Of the agents available in the United States, the greatest human experience has been with beclomethasone. The results have been extremely favorable, making beclomethasone the preferred agent. Triamcinolone and flunisolide have not been studied in humans, although animal studies are favorable.

Systemic Corticosteroids Systemic corticosteroids (oral and injectable) may also be needed to treat severe asthma attacks during pregnancy. These agents may be used safely and should not be withheld due to fear of adverse effects on a patient's pregnancy. Human studies have shown only a slight increase in low birth weight and premature births in patients receiving systemic corticosteroids for prolonged periods throughout pregnancy. There has been no evidence of increased birth defects secondary to the use of corticosteroids during pregnancy in large human studies.

Nedocromil Sodium Nedocromil sodium resembles cromolyn and is another nonsteroidal anti-inflammatory. At this time there is no human experience to refer to, although animal studies are favorable. For this reason, cromolyn sodium would be the preferred alternative to inhaled corticosteroids.

Medications for Related Conditions during Pregnancy

Allergic Rhinitis and Sinusitis

There is a high incidence of allergic rhinitis and sinusitis in patients with bronchial asthma. There is a greater frequency of sinusitis during pregnancy. Upper and lower respiratory tract infections, including pneumonia, may occur during pregnancy. Treatment of these conditions should not be delayed since they may trigger more severe asthma attacks. Many medications can be used safely for these conditions, while some should definitely be avoided.

Intranasal Sprays

Allergic rhinitis such as hay fever may be treated with intranasal topical corticosteroid sprays as well as intranasal cromolyn sodium. Of the intranasal steroids, beclomethasone is the preferred agent due to its large human experience. The aerosol spray treatments are preferred over oral antihistamines.

Antibiotics

Antibiotics may be needed during pregnancy to treat specific infections. Indiscriminate use of antibiotics should be avoided, especially when viral infection is most likely as in the common cold. Tetracycline, sulfonamides (in late pregnancy), and the quinalones should be avoided during pregnancy. Penicillin and its derivatives such as amoxicillin may be used safely. For penicillin allergic patients erythromycin may be substituted. Sulfonamides may be used in early or midpregnancy.

Antihistamines

Antihistamines such as chlorpheniramine and tripelennamine may be used safely during pregnancy in patients unresponsive to the topical sprays. One adverse effect of these antihistamines is drowsiness. The newer nonsedating antihistamines such as terfenadine, loratadine, and astemizole have not been studied in humans during pregnancy.

Decongestants

Decongestants may be indicated to relieve persistent and severe nasal symptoms in rhinitis and the common cold. Human experience with pseudoephredrine has been favorable, although animal studies have shown fetal abnormalities. An alternative is oxymetazoline nasal spray or drops for a period not to exceed five days. One drawback to oxymetazoline is a patient's tendency to become dependent on its decongestant effect from prolonged use.

Expectorants

Expectorants may be prescribed by the physician to help loosen thick secretions. Iodides, a common ingredient in expectorants, should be avoided during pregnancy and are being withdrawn by the FDA. Guaifenesin may be used safely during pregnancy to help mobilize secretions. Severe cough from lower respiratory tract infections may be harmful and traumatic. A cough suppressant, dextromethorphan, has been used with favorable results during pregnancy. It should be noted, however, that cough may serve a useful purpose in clearing mucus and in many instances should not be suppressed. Cough may also signal that asthma has become more severe. This should be acknowledged by reviewing the patient's history and physical exam in conjunction with airflow measurements. It is vital to be aware of the ingredients in any cough mixture. Many preparations contain several medications including antihistamines, alcohol, and aspirin which should be avoided by most individuals with asthma.

The Common Cold

Some simple measures can help treat the common cold. A buffered saline nasal spray can moisturize irritated nasal membranes and flush dried mucus. Patients should force fluids; warm fluids provide some relief from nasal congestion. Bed rest can also help and often shortens recovery. For severe symptoms the decongestants and cough medications noted above can help. All treatment should be directed by the patient's physician. Any persistent fever, sore throat, sinus pain, and discharge should prompt quick examination and treatment. Cultures can be obtained to document bacterial infections that will require antibiotic therapy.

In many instances a common cold triggers increased bronchial narrowing, which may occur through throat and bronchial infections as well as through irritation of the bronchial tubes by postnasal discharge. Peak flows should be monitored closely during colds to identify when bronchoconstriction occurs. Early recognition of bronchial narrowing allows the patient and physician to begin a treatment plan that reverses bronchoconstriction before a severe attack can occur. This plan may include an increase in the number of sprays of a topical corticosteroid or a course of oral steroid.

Labor and Delivery

All of the preferred asthma medications can be continued during labor. In general, patients should continue their normal asthma medications throughout labor. Corticosteroids may also be given in those patients who have been steroid dependent and may have adrenal insufficiency. The type of delivery will be determined by the patient's obstetrician. In patients with severe or unstable asthma, a cesarean section maybe necessary.

A thirty-four-year-old woman with severe asthma has been under my care for ten years. Five years ago she asked me if I thought it was medically safe for her to have a child. The patient had been hospitalized for asthma and had required frequent courses of oral corticosteroids. Her daily treatment plan included regular B-agonist, inhaled corticosteroid, cromolyn sodium, and theophylline. We decided to do a detailed pulmonary function test to help in the decision. I knew that she was highly motivated and involved in her care. She was also extremely compliant with her medication routine and called whenever there was a significant drop in her peak flow. I reviewed her breathing tests and found that her lung capacity was 70 percent of normal after she used her bronchodilator spray. The patient's oxygen level was near normal. I told her that I thought she could become pregnant. During her pregnancy she required oral corticosteroids several times and maintained her usual medications. I spoke frequently with her obstetrician. The patient's asthma remained severe but did not worsen and she delivered a healthy baby girl by cesarean section. Her asthma has remained severe and during office visits we sometimes refer to her daughter as the "miracle baby." When I look back at all the factors that had to be considered, I am sure I would make the same decision.

Should Allergy Treatments Be Started or Continued

Immunotherapy (also called desensitization) has been helpful in reducing asthma attacks in allergic patients, although adverse reactions to allergy injections may occur in sensitive individuals. A severe, total body reaction such as anaphylaxis would threaten a developing fetus. Anaphylaxis has also been reported to induce labor. For these reasons it is recommended that no allergy treatment or immunotherapy be started during pregnancy.

In patients who have reached maintenance therapy in which dosages of allergens injected are not increased and who are not known to have reactions, immunotherapy may continue as prescribed by the patient's physician. Patients who are extremely sensitive and who have had systemic reactions such as anaphylaxis are best not treated.

Is Flu Vaccine Safe during Pregnancy?

A killed vaccine, such as influenza vaccine, does not pose a threat during pregnancy. In fact, it is a good idea for patients with moderate to severe asthma to receive influenza vaccine in order to avoid this severe infection that may exacerbate their disease. This vaccine should be administered before December 1st in order to allow enough time for antibody levels to become effective.

After Delivery

Nursing

Asthma medications are commonly found in breast milk but that should not keep asthmatic mothers from breast-feeding. The inhaled medications (B2-agonists, inhaled corticosteroids, cromolyn sodium) do not reach significant levels in breast milk and should have little, if any, effect on an infant. Oral corticosteroids are secreted in breast milk but only a small fraction of the mother's dosage reaches the infant. Prednisone and prednisolone are also considered compatible with breast-feeding. Theophylline is secreted in breast milk but less than 1 percent of the mother's dose ever reaches the child. In rare instances, excessive irritability has been reported in infants being breast-fred by mothers receiving theophylline. If that occurs and the mother's asthma is well controlled, it is usually possible to interrupt theophylline and adjust other medications.

Avoiding Complications during Pregnancy

To reduce complications that may adversely affect the mother and developing child, asthma should be well controlled before and during pregnancy. Uncontrolled asthma may reduce oxygen delivery to the fetus and lead to serious complications. Treatment of asthma during pregnancy is similar to the general treatment plan .Most of the asthma medications are clearly safe during pregnancy and should be used normally. Unfortunately, their fear of medication side effects during pregnancy has prompted many asthmatic patients to eliminate their medicines, thus increasing their risk of complications. Through patient education and communication with the physician as well as careful use of asthma medications, the risk of complications for pregnant asthmatics can be greatly reduced.