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INTRODUCTION — Asthma is the most common condition affecting the lungs during pregnancy. At any given time, up to 8 percent of pregnant persons have asthma. Many pregnant people worry about how the changes of pregnancy will affect their asthma and if asthma treatments will harm the baby. With appropriate asthma therapy, most patients 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 patient receives regular medical care and follows the treatment plan closely. Before becoming pregnant, individuals with asthma should discuss their condition with a healthcare provider. Patients 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 education: Asthma treatment in adolescents and adults (Beyond the Basics)" and "Patient education: How to use a peak flow meter (Beyond the Basics)" and "Patient education: Inhaler techniques in adults (Beyond the Basics)" and "Patient education: Trigger avoidance in asthma (Beyond the Basics)".)
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. While older information suggested that asthma worsened in about one-third of pregnant persons, improved in one-third, and remained stable in one-third, more recent information suggests that 40 percent of pregnant persons may experience worse asthma control during pregnancy while the remainder have the same level of control.
Other patterns that have been observed include:
●Among patients 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 patients 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. Modifiable risk factors that increase risk of asthma attack during pregnancy include smoking, being overweight, depression or anxiety, poorly controlled asthma, and poor adherence to asthma medication. 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 patients stop using asthma-controlling drugs when they realize they are pregnant, increasing their risk for attacks.
EFFECTS OF ASTHMA ON PREGNANCY AND BABY — Patients who have asthma have a small increase in the risk for certain complications of pregnancy, although the reasons for this are unknown. Compared with patients who do not have asthma, individuals with asthma are slightly more likely to have one or more of the following pregnancy complications:
●High blood pressure or preeclampsia (see "Patient education: Preeclampsia (Beyond the Basics)")
●A premature delivery (see "Patient education: Preterm labor (Beyond the Basics)")
●A cesarean delivery (see "Patient education: C-section (cesarean delivery) (Beyond the Basics)")
●A baby that is small for its age
However, the vast majority of pregnant people 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.
ASTHMA TREATMENT DURING PREGNANCY — During pregnancy, care of patients 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 persons is very similar to asthma treatment in those who are not pregnant. Management of asthma during pregnancy has several key components, which are most successful when used together:
●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 patients 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 expiratory 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 education: How to use a peak flow meter (Beyond the Basics)".)
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 patients who have asthma. Patients 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 patients who are also having asthma symptoms or an asthma attack.
●Non-stress testing is sometimes recommended after 32 weeks of pregnancy for patients 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 education: Asthma treatment in adolescents and adults (Beyond the Basics)" and "Patient education: Inhaler techniques in adults (Beyond the Basics)".)
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 (from hair, fur, or feathers), house dust, and nonspecific irritants, such as tobacco smoke, strong perfume, and pollutants.
●If allergic to house dust mites, cover mattresses and pillows with plastic covers or special mite-proof encasings. Avoid sleeping on upholstered furniture (eg, couches, recliners).
●Pregnant persons should not smoke or permit smoking in their home.
●People 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 education: Influenza symptoms and treatment (Beyond the Basics)".)
●Available data are reassuring for the safety of COVID-19 vaccines during pregnancy, and the benefits of receiving a vaccine to prevent COVID-19 illness, which may be particularly severe in pregnant persons and may increase pregnancy complications, likely outweigh any potential risks. The CDC notes the increased risk of severe disease in pregnant persons and states that pregnant people may choose to be vaccinated but does not provide a formal recommendation about vaccination during pregnancy. (See "COVID-19: Overview of pregnancy issues", section on 'Vaccination in people planning pregnancy and pregnant or recently pregnant people'.)
For more information about trigger avoidance, (see "Patient education: Trigger avoidance in asthma (Beyond the Basics)").
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 persons for many years, and the information available suggests 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.
Bronchodilators — Short-acting bronchodilators rapidly relieve asthma symptoms by relaxing the airways. They include albuterol (Proventil, Ventolin) and levalbuterol (Xopenex). These short-acting bronchodilators appear to be safe during pregnancy. Several studies have shown that the babies of people who used these drugs during pregnancy had no increase in health problems when compared to the babies of mothers who did not. In contrast, inhaled epinephrine products (eg, Asthmanefrin, Primatene Mist), which are now available over the counter, are not as effective as albuterol; are associated with adverse effects, such as chest pain, increased blood pressure, and rapid heart rate; and should not be used.
Longer-acting bronchodilators, such as salmeterol and formoterol, are used for long-term control of asthma in combination with an inhaled glucocorticoid (eg, Advair and Symbicort). Although less safety data are available for long-acting bronchodilators in pregnancy than for several other types of asthma medications, they are often used because of their effectiveness in controlling asthma and chemical similarities to the short-acting bronchodilators mentioned above. National guidelines now recommend inhaled glucocorticoids combined with formoterol as both regular preventive therapy and as-needed reliever therapy in patients with moderate to severe asthma, but this strategy has not been evaluated in pregnant persons. The benefits of longer-acting bronchodilators (which should be used in combination with an inhaled glucocorticoid) are greater than any proven risks in pregnancy.
Glucocorticoids — Glucocorticoids are used to treat many conditions in addition to asthma. Experience from their use in pregnant persons 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 (Qvar), budesonide (Pulmicort), and fluticasone (Flovent). A number of commonly used inhalers combine a glucocorticoid with a long-acting bronchodilator (eg, Advair, Symbicort, Dulera, Breo).
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.
In addition, 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.
Patients 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. Individuals who take glucocorticoid pills frequently during pregnancy may 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 and fluticasone are thought to be among the safest inhaled glucocorticoids for use in pregnant persons. 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 now rarely used for asthma since the introduction of inhaled glucocorticoids, which are more effective and cause fewer side effects than theophylline.
Cromolyn — Cromolyn appears to be a safe drug during pregnancy, although it is not as effective as inhaled glucocorticoids in controlling asthma. In most countries, it is only available in a nebulized form and is rarely used.
Leukotriene modifiers — Some drugs help control asthma by blocking the leukotriene pathway, which plays an important role in asthma. These drugs include montelukast (Singulair), zafirlukast (Accolate), and zileuton (Zyflo). Three studies have shown that infants of pregnant persons who took montelukast or zafirlukast had no increase in major birth defects or adverse outcomes. Between these two, more reassuring information is available for montelukast.
Little is known about the safety of zileuton in pregnant persons. 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, cetirizine, and fexofenadine have the most reassuring data 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 no more than three 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 persons who do not have high blood pressure or placental problems.
Immunotherapy — Immunotherapy refers to regular injections (allergy shots) or pills used under the tongue (sublingual immunotherapy or SLIT) 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 persons.
It is probably safe for patients who are already receiving immunotherapy to continue receiving allergy shots or SLIT during pregnancy. Patients who are not using immunotherapy at the time they become pregnant generally should not start immunotherapy until after delivery.
Biologic agents – "Biologic agents" are used occasionally for patients with severe asthma. These drugs, which are given by either subcutaneous or intravenous injection, are antibodies against chemicals thought to be important in some patients with asthma. Examples of these biologic agents include omalizumab, mepolizumab, and dupilumab. At present, animal data and limited human data have not identified problems with use of these drugs during pregnancy. Although it is probably advisable not to start a biologic agent during pregnancy, it is reasonable to continue a biologic agent during pregnancy in patients with severe asthma who have had a good response to the drug.
LABOR, DELIVERY, AND THE POSTPARTUM PERIOD — Pregnant persons 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.
For patients with asthma, the drug oxytocin (Pitocin) is the preferred agent to stimulate uterine contractions, induce labor, and to control bleeding after delivery. During labor and delivery, epidural or spinal anesthesia may be safer than general anesthesia (being put to sleep) for patients with asthma.
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, patients with asthma are encouraged to breastfeed because there are a number of other benefits for both her and her infant. (See "Patient education: Deciding to breastfeed (Beyond the Basics)".)
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 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.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)
Patient education: How to use a peak flow meter (Beyond the Basics)
Patient education: Inhaler techniques in adults (Beyond the Basics)
Patient education: Trigger avoidance in asthma (Beyond the Basics)
Patient education: Preeclampsia (Beyond the Basics)
Patient education: Preterm labor (Beyond the Basics)
Patient education: C-section (cesarean delivery) (Beyond the Basics)
Patient education: Influenza symptoms and treatment (Beyond the Basics)
Patient education: Deciding to breastfeed (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Maternal adaptations to pregnancy: Dyspnea and other physiologic respiratory changes
Management of asthma during pregnancy
Asthma in pregnancy: Clinical course and physiologic changes
Primary prevention of allergic disease: Maternal diet in pregnancy and lactation
Recognition and management of allergic disease during pregnancy
The following organizations also provide reliable health information.
●National Library of Medicine
●American Academy of Allergy, Asthma, and Immunology
●American College of Allergy, Asthma, and Immunology
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