Asthma and pregnancy

Asthma and pregnancy

Authors
Steven E Weinberger, MD
Michael Schatz, MD, MS
Mitchell P Dombrowski, MD
Section Editors
Charles J Lockwood, MD
Peter J Barnes, DM, DSc, FRCP, FRS
Deputy Editors
Helen Hollingsworth, MD
Vanessa A Barss, MD

Disclosures

Last literature review version 19.3: Fri Sep 30 00:00:00 GMT 2011 | This topic last updated: Tue Apr 20 00:00:00 GMT 2010 (More)
INTRODUCTION — Asthma is the most common condition affecting the lungs during pregnancy. At any given time, up to 8 percent of pregnant women have asthma. Many women worry about how the changes of pregnancy will affect their asthma and if asthma treatments will harm the baby. With appropriate asthma therapy, most women can breathe easily, have a normal pregnancy, and deliver a healthy baby. Overall, the risk of poorly controlled asthma is much greater than the risk of taking medications to control asthma.

Asthma therapy during pregnancy is most successful when a woman receives regular medical care and follows her treatment plan closely. Before becoming pregnant, women with asthma should discuss their condition with a healthcare provider. Women who discover that they are pregnant should continue their asthma medications. Suddenly stopping asthma medications could be harmful to you and your baby.

Topic reviews about asthma in non-pregnant adults are available separately. (See “Patient information: Asthma treatment in adolescents and adults” and “Patient information: How to use a peak flow meter” and “Patient information: Asthma inhaler techniques in adults” and “Patient information: Trigger avoidance in asthma”.)

SEVERITY OF ASTHMA DURING PREGNANCY — The severity of asthma during pregnancy varies from one woman to another. Unfortunately, it is difficult to predict the course that asthma will follow in a woman’s first pregnancy. During pregnancy, asthma worsens in about one-third of women, improves in one-third, and remains stable in one-third.

Other patterns that have been observed include:

Among women whose asthma worsens, an increase in symptoms is often seen between weeks 29 and 36 of pregnancy.
Asthma is generally less severe during the last month of pregnancy.
Labor and delivery do not usually worsen asthma.
Among women whose asthma improves, the improvement typically progresses gradually throughout pregnancy.
The severity of asthma symptoms during the first pregnancy is often similar in subsequent pregnancies.
Factors affecting risk of attacks — The factors that increase or decrease the risk of asthma attacks during pregnancy are not entirely clear. The likelihood of these attacks is not constant throughout pregnancy; attacks seem to be most likely during weeks 17 through 24 of pregnancy. The cause for this pattern is unknown, although it may be because some women stop using asthma-controlling drugs when they realize they are pregnant, increasing their risk for attacks.

EFFECTS OF ASTHMA ON PREGNANCY AND BABY — Women who have asthma have a small increase in the risk for certain complications of pregnancy, although the reasons for this are unknown. Compared to women who do not have asthma, women with asthma are slightly more likely to have one or more of the following pregnancy complications:

High blood pressure or preeclampsia (see “Patient information: Preeclampsia”)
A premature delivery (see “Patient information: Preterm labor”)
A cesarean delivery (see “Patient information: C-section (cesarean delivery)”)
A baby that is small for its age
However, the vast majority of women with asthma and their babies do NOT have any complications during pregnancy. Good control of asthma during pregnancy reduces the risk of complications.

CARE BEFORE PREGNANCY — If you take prescription or non-prescription medications, these should be reviewed with a healthcare provider. Some medications are safe during pregnancy while others are not. In some cases, an alternate medication can be substituted for an unsafe drug.

ASTHMA TREATMENT DURING PREGNANCY — During pregnancy, care of women with asthma is sometimes shared between an asthma specialist and an obstetrical provider. Visits with an asthma specialist are scheduled based upon the severity of asthma during pregnancy. Asthma treatment in pregnant women is very similar to asthma treatment in those who are not pregnant. Therapy during pregnancy has several key components, which are most successful when used together:

Monitoring

Mother’s lung function — Normal lung function is important to a mother’s health and to her baby’s well-being. Lung function can be monitored in a healthcare provider’s office or hospital. Lung function tests, such as spirometry, are useful for distinguishing the shortness of breath associated with a worsening of asthma from the normal shortness of breath that many women experience during pregnancy.
Asthma can also be monitored at home by using a simple device called a peak flow meter that assesses airway narrowing due to asthma. Depending on the frequency of asthma symptoms, a healthcare provider may recommend measuring the peak flow rate (PEFR) once or twice per day: once upon awakening and again 12 hours later. Decreasing flow rates usually signal a worsening of asthma and a need for more intensive therapy, even if the patient is feeling well. (See “Patient information: How to use a peak flow meter”.)
Baby’s well-being — A baby’s well-being is monitored in a variety of ways during regular medical visits throughout pregnancy. These visits are particularly important for women who have asthma. Women should be aware of their baby’s movements. If your baby is not moving normally, contact your obstetrical provider immediately. This is especially true for women who are also having asthma symptoms or an asthma attack.

Non-stress testing is sometimes recommended after 32 weeks of pregnancy for women who have frequent asthma symptoms or attacks. The test is performed to assess the baby’s condition. It is done by monitoring the baby’s heart rate with a small ultrasound device that is placed on the mother’s abdomen. The baby’s heart rate should increase when it moves. The test is considered reassuring if two or more fetal heart rate increases are seen within a 20 minute period. Further testing may be needed if these increases are not observed after monitoring for 40 minutes.
Ultrasound examination to check the baby’s growth and activity, and also the amount of amniotic fluid around the baby, is sometimes performed.
Education — Learning more about asthma may help you manage your symptoms better, prevent attacks, and react quickly when attacks do occur. This education can be particularly reassuring and useful during pregnancy. Asthma education teaches strategies to recognize the signs and symptoms of asthma, avoid factors that trigger attacks, and use asthma-controlling drugs correctly. (See “Patient information: Asthma treatment in adolescents and adults” and “Patient information: Asthma inhaler techniques in adults”.)

Avoiding triggers — Several simple steps can help control environmental factors that worsen asthma and trigger attacks. These include:

Avoid exposure to specific allergens that are known to cause your asthma symptoms, especially pet dander (such as fur or feathers), house dust, and nonspecific irritants, such as tobacco smoke, strong perfume, and pollutants
Cover mattresses and pillows with special casings to reduce exposure to dust mites. Avoid sleeping on upholstered furniture (eg, couches, recliners).
Pregnant women should not smoke or permit smoking in their home.
Women who will be pregnant during flu season (the winter months in most areas) should get a flu shot; there are no known risks of the flu shot for a developing fetus. Flu shots are generally given once per year in the fall. (See “Patient information: Influenza symptoms and treatment”.)
For more information about trigger avoidance, (see “Patient information: Trigger avoidance in asthma”).

Medications — With a few exceptions, the medications used to treat asthma during pregnancy are similar to the medications used to treat asthma at other times during a person’s life. The type and dose of asthma medications will depend upon many factors. In general, inhaled drugs are recommended because there are limited body-wide effects in the mother and the baby. It may be necessary to adjust the type or dose of drugs during pregnancy to compensate for changes in the woman’s metabolism and changes in the severity of asthma.

It is difficult to prove that asthma-controlling drugs are completely safe during pregnancy. However, asthma medications have been used by pregnant women for many years, suggesting that most of them probably carry little or no risk for the mother or baby. Specific guidance about medication safety is discussed in the section below (see ‘Asthma medications’ below).

It is important to consider the unknown (but likely small) risk of asthma-controlling drugs compared to the potentially serious harm of undertreated asthma. Severe asthma attacks can reduce the oxygen supply to the baby. In most cases, undertreated asthma poses a far greater risk to both the mother and the baby than the use of asthma-controlling drugs. Therefore, it is important to take asthma medications on a regular basis to prevent asthma symptoms.

ASTHMA MEDICATIONS

Bronchodilators — Short-acting bronchodilators rapidly relieve asthma symptoms by relaxing the airways. They include albuterol (Proventil®, Ventolin®), metaproterenol (Alupent®), terbutaline, and other drugs. Short-acting bronchodilators appear to be safe during pregnancy. One study showed that the babies of women who used these drugs during pregnancy had no increase in health problems when compared to the babies of mothers who did not.

Longer-acting bronchodilators, such as salmeterol (Serevent®) and formoterol (Foradil®), are used for long-term control of asthma in combination with an inhaled glucocorticoid (eg, Advair® and Symbicort®), but not for rapid relief of symptoms. There are not enough data about the safety of long-acting bronchodilators to know if they are safe for use during pregnancy or not. Women who take a long-acting bronchodilator should discuss the risks and benefits of use during pregnancy with their healthcare provider.

Glucocorticoids — Glucocorticoids are used to treat many conditions in addition to asthma. Experience from their use in pregnant women suggests that these drugs are generally safe for both the mother and the baby. The glucocorticoids include pills such as prednisone and inhaled drugs such as beclomethasone (Beclovent®, Vanceril®, and others), budesonide (Pulmicort®), and fluticasone (Flovent®).

Oral glucocorticoids — Some studies have suggested that there may be a very small increased risk of cleft lip or cleft palate in the babies of mothers who took oral glucocorticoid medications during the first 13 weeks of pregnancy. Two studies found a slightly increased risk of premature delivery, and one study found a slightly increased risk of having a low birth weight baby. However, the researchers could not rule out the possibility that these effects were related to the severity of asthma and not to the use of the drug.

However, all of the above risks are probably smaller than the risk of not treating severe asthma, which could be life-threatening for the mother and the baby.

Women who take glucocorticoid pills during pregnancy may be more likely to develop gestational diabetes and high blood pressure, although these conditions can be detected and managed with regular medical visits. Women who take glucocorticoid pills frequently during pregnancy will need glucocorticoids by IV (into a vein) during labor and delivery.

Inhaled glucocorticoids — The information about inhaled glucocorticoids is quite reassuring. A variety of inhaled glucocorticoids have been used during pregnancy. Budesonide is thought to be one of the safest inhaled glucocorticoids. Beclomethasone has also been used extensively during pregnancy.

Theophylline — Theophylline (Slo-bid®, Theo-Dur®, and others) has been used for many years during pregnancy without any apparent complications, suggesting that it is safe during pregnancy. However, theophylline is used less often for asthma since the introduction of inhaled glucocorticoids. Inhaled glucocorticoids are more effective and cause fewer side effects than theophylline.

Cromolyn sodium — There was no increase in birth defects or other pregnancy complications in one study of women who took cromolyn sodium during pregnancy. Cromolyn appears to be a safe drug during pregnancy, although it is not as effective as inhaled glucocorticoids in controlling asthma.

Leukotriene modifiers — Some drugs help control asthma by blocking the leukotriene pathway, which plays an important role in asthma. These drugs include zafirlukast (Accolate®), montelukast (Singulair®), and zileuton (Zyflo™). One small study showed that infants of pregnant women who took a leukotriene modifier had no increase in major birth defects or adverse outcomes.

Little is known about the safety of zileuton in pregnant women. If you are taking zileuton and planning to become pregnant, discuss whether to stop zileuton with your doctor.

Antihistamines — Although antihistamines are not used to directly treat asthma, they may be used to treat the allergies that often accompany asthma. These drugs include diphenhydramine (Benadryl®), chlorpheniramine (Chlor-Trimeton® and others), loratadine (Claritin®), fexofenadine (Allegra®), and cetirizine (Zyrtec®).

Studies in both animals and humans suggest that antihistamines cause no increase or only a very small increase in the risk for birth defects when taken during pregnancy. Of the currently available preparations, chlorpheniramine (which can be sedating), loratadine, or cetirizine are considered the antihistamines of choice for use during pregnancy.

Decongestants — Decongestants are not used for the treatment of asthma, but may be used to treat the symptoms of upper airway allergies. Pseudoephedrine (Sudafed®) is a decongestant that is commonly available.

Most studies examining the safety of decongestants during pregnancy have been small, making it difficult to draw clear-cut conclusions. Until more information is available, it is probably safest to use a nasal spray decongestant (for 3 days in a row) rather than to take an oral decongestant during the first 13 weeks. After the first 13 weeks, the use of pseudoephedrine is thought to be safe in pregnant women who do not have high blood pressure or placental problems.

Immunotherapy — Immunotherapy refers to regular injections (allergy shots) that are given to reduce a person’s sensitivity to allergens. This therapy appears to be safe during pregnancy, although it carries a very small risk of a severe allergic reaction (anaphylaxis) in any person, including pregnant women.

It is probably safe for women who are already receiving immunotherapy to continue receiving allergy shots during pregnancy. Women who are not using immunotherapy at the time they become pregnant generally should not start immunotherapy until after delivery.

LABOR, DELIVERY, AND THE POSTPARTUM PERIOD — Pregnant women with asthma should discuss their labor and delivery plans with their healthcare provider. Asthma may affect a provider’s choice of medications commonly used during labor, delivery, and the postpartum period.

Women with asthma can be treated with the drug oxytocin (Pitocin®) to induce labor and to control bleeding after delivery. During labor and delivery, epidural anesthesia is preferred over general anesthesia for women with asthma because epidural anesthesia reduces the demands on the lungs.

If general anesthesia becomes necessary (eg, for emergency cesarean section), a general anesthetic that promotes dilation of airways is recommended.

Breastfeeding — Breastfeeding appears to lower the risk that an infant will have recurrent episodes of wheezing during the first two years of life. This is probably due to the fact that infants who breastfeed have a reduced number of respiratory infections during this period. Respiratory infections are a common cause of wheezing in infants.

It is less clear if breastfeeding reduces the risk that the infant will later develop asthma. However, women with asthma are encouraged to breastfeed because there are a number of other benefits for both her and her infant. (See “Patient information: Deciding to breastfeed”.)

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed every four months on our web site (www.uptodate.com/patients).

Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

 

The following organizations also provide reliable health information.

National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)

American Academy of Allergy, Asthma, and Immunology
(www.aaaai.org/patients.stm)

National Heart, Lung, and Blood Institute
(www.nhlbi.nih.gov/health/prof/lung/asthma/astpreg.htm)

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REFERENCES
Tata LJ, Lewis SA, McKeever TM, et al. Effect of maternal asthma, exacerbations and asthma medication use on congenital malformations in offspring: a UK population-based study. Thorax 2008; 63:981.
Dombrowski MP, Schatz M, ACOG Committee on Practice Bulletins-Obstetrics. ACOG practice bulletin: clinical management guidelines for obstetrician-gynecologists number 90, February 2008: asthma in pregnancy. Obstet Gynecol 2008; 111:457.
Bakhireva LN, Jones KL, Schatz M, et al. Asthma medication use in pregnancy and fetal growth. J Allergy Clin Immunol 2005; 116:503.