Patient information: Pregnancy and asthma

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 result in the developing baby not getting enough oxygen.

Topics 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 (graph 1). 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: 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

These recommendations apply to any woman who is considering pregnancy.

• All women should take a supplement containing at least 400 mcg of folic acid (the amount in a prenatal vitamin). Taking folic acid can reduce the risk of a specific birth defect, called a neural tube defect. Folic acid should be started before trying to conceive and continued until at least the end of the first trimester. Most prenatal vitamins contain adequate folic acid.
• Women should stop smoking and consuming alcohol or any recreational drugs (eg, marijuana) before trying to become pregnant.
• If a woman takes 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.
• Caffeine intake should be limited to less than 250 mg per day while trying to become pregnant and during pregnancy. Table 1 lists the caffeine content of several common beverages (table 1)

• Blood testing for rubella (German measles), varicella (chicken pox), HIV, hepatitis B, and inherited genes (eg, cystic fibrosis) may be recommended before pregnancy.

CARE DURING PREGNANCY

During pregnancy, care of women with asthma is sometimes shared between an asthma specialist and an obstetrical provider. Visits with the asthma specialist are scheduled based upon the severity of asthma during pregnancy. Most women are seen by their obstetrical provider every two to four weeks until 28 weeks of pregnancy. Between 28 and 36 weeks, most women are seen every two weeks. Women are usually seen once per week between 36 weeks and delivery. At every visit, blood pressure and urine testing will be done.

To monitor the baby's growth during pregnancy, it is important to have an accurate due date. Women who cannot remember the date of their last menstrual period or are unsure of when the baby was conceived should have an ultrasound before 12 weeks of pregnancy; the due date is most accurate when measured during this time.

After 10 to 12 weeks of pregnancy, the baby's heart rate will be measured at every visit. An ultrasound is usually recommended between 18 and 20 weeks of pregnancy to ensure that the baby is growing and developing normally.

Women who require glucocorticoid pills (eg, prednisone) during pregnancy may have an ultrasound to monitor the baby's growth every four weeks after 18 to 20 weeks of pregnancy.

Asthma treatment — 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. Home monitoring often provides important information when asthma symptoms worsen, typically during the night or upon awakening.

Pregnant women can monitor their lung function at home by using a simple device that measures the peak expiratory flow rate (PEFR). Depending on the frequency of attacks, a healthcare provider may recommend measuring this rate 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".)

Lung function tests performed in a clinician's office are also 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.

• Baby's well-being — A baby's well-being is carefully monitored during regular medical visits throughout pregnancy. These visits are particularly important for women who have asthma.

In addition, women who are greater than 24 weeks pregnant should monitor the baby's movements. If the 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 device that is placed on the mother's abdomen. The device uses sound waves (ultrasound) to measure the baby's heart rate over time, usually for 15 to 30 minutes. Normally, the baby's baseline heart rate should be between 120 and 160 beats per minute. The baby's heart rate should increase periodically by at least 15 beats per minute above the baseline heart rate for 15 seconds.

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.

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

• Avoid exposure to specific allergens, 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".

Education — Learning about asthma enables people to better manage their symptoms, prevent attacks, and react 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. With these tools, an individualized treatment plan for sudden attacks can be created.

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.

• Safety of asthma-controlling drugs — 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) risks of asthma-controlling drugs compared to the potentially serious harm of undertreated asthma. Asthma attacks can reduce the oxygen supply to the baby. Therefore, it is important to take asthma medications on a regular basis to prevent asthma symptoms. In most cases, undertreated asthma poses a far greater risk to both the mother and the baby than the use of asthma-controlling drugs.

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. Longer-acting bronchodilators, such as salmeterol (Serevent®) and formoterol (Foradil®), are important for control of asthma but do not rapidly relieve asthma symptoms.

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 [1].

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, either alone or in a combination treatment (eg, Advair and Symbicort) 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), triamcinolone (Azmacort®), flunisolide (AeroBid®), 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 [2]. 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 [3]. 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 [4]. Women who taking glucocorticoid pills 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 [5]. 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 [6].

Little is known about the safety of zileuton in pregnant women.

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.

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 promote 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. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: A guide to pregnancy
Patient information: Asthma treatment in adolescents and adults
Patient information: How to use a peak flow meter
Patient information: Asthma inhaler techniques in adults
Patient information: Trigger avoidance in asthma
Patient information: Preeclampsia
Patient information: Preterm labor
Patient information: Cesarean delivery
Patient information: Influenza symptoms and treatment
Patient information: Deciding to breastfeed

Professional Level Information:
Dyspnea during pregnancy
Management of asthma during pregnancy
Physiology and clinical course of asthma in pregnancy
Primary prevention of allergic disease: Maternal avoidance diets in pregnancy and lactation
Recognition and management of allergic disease during pregnancy
Patient information: A guide to pregnancy

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• American Lung Association

      (www.lungusa.org)

• Canadian Lung Association

     (www.lung.ca)

• 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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