Asthma is one of the most common chronic respiratory conditions affecting women of childbearing age, with an estimated prevalence of 4% to 8% in pregnant women globally. When left uncontrolled, asthma during pregnancy poses significant risks not only to the mother but also to the developing fetus. Proper management is therefore critical to ensure optimal maternal and neonatal outcomes.
Understanding Asthma in Pregnancy – Pathophysiology and Prevalence
Asthma is a chronic inflammatory disorder of the airways characterized by bronchial hyperresponsiveness, airflow limitation, and variable symptoms such as wheezing, shortness of breath, chest tightness, and cough. During pregnancy, hormonal, immunological, and mechanical changes can alter the course of asthma, leading to variable disease expression. Approximately one-third of pregnant women with asthma experience improvement in symptoms, one-third see no change, and the remaining one-third report worsening of symptoms, typically during the second and third trimesters.
The hormonal shifts in pregnancy—particularly increases in estrogen and progesterone—play a significant role. Progesterone enhances respiratory drive, which may improve ventilation but can also exacerbate breathlessness. Additionally, pregnancy induces a T-helper 2 (Th2) immune bias to support fetal tolerance, which may increase susceptibility to allergic inflammation and worsen asthma in some women. Mechanical changes such as upward displacement of the diaphragm reduce functional residual capacity, though total lung capacity is generally preserved.
Understanding these physiological changes is crucial because they directly influence asthma symptom perception and pulmonary function testing interpretation during pregnancy.
Impact of Uncontrolled Asthma on Maternal and Fetal Health
Uncontrolled asthma has serious implications. Maternal risks include preeclampsia, gestational hypertension, hyperemesis gravidarum, vaginal hemorrhage, and the need for cesarean delivery. Fetal complications are equally concerning and include intrauterine growth restriction (IUGR), preterm birth, low birth weight, neonatal hypoxia, and even perinatal mortality.
The primary mechanism linking asthma to adverse outcomes is chronic maternal hypoxemia. When asthma is unmanaged, intermittent or persistent oxygen desaturation reduces oxygen delivery to the placenta, compromising fetal growth and development. Additionally, systemic inflammation associated with asthma may contribute to placental dysfunction and preterm labor.
It is important to emphasize that the risks associated with uncontrolled asthma far outweigh those of properly managed pharmacologic treatment. Numerous studies, including large cohort analyses, have demonstrated that appropriate asthma therapy improves both maternal and fetal well-being.
Diagnosis and Assessment of Asthma During Pregnancy
Diagnosing asthma in pregnant women requires a thorough clinical evaluation, especially since symptoms like shortness of breath and fatigue are common in normal pregnancy and may be mistakenly attributed to gestational changes.
Key diagnostic steps include:
- Medical history: Documenting previous asthma diagnosis, triggers, symptom frequency, past exacerbations, hospitalizations, and prior medication use.
- Physical examination: Listening for wheezing, prolonged expiration, or decreased breath sounds.
- Pulmonary function testing (PFT): Spirometry remains the gold standard for diagnosing and monitoring asthma. The test measures forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). A reduced FEV1/FVC ratio (<0.7) confirms airflow obstruction, and reversibility with bronchodilators supports an asthma diagnosis.
- Peak expiratory flow rate (PEFR) monitoring: This can be used at home for ongoing assessment, especially when spirometry is not readily accessible.
Symptom severity is classified into four categories—intermittent, mild persistent, moderate persistent, and severe persistent—based on symptom frequency, nighttime awakenings, use of rescue medication, and impact on daily activities. This classification guides treatment decisions.
Developing an Asthma Action Plan
Every pregnant woman with asthma should have a personalized asthma action plan developed in collaboration with her healthcare provider. This written plan includes:
- Daily medication regimens.
- Instructions for recognizing worsening symptoms.
- Steps to take during an asthma exacerbation.
- When to seek emergency care.
The action plan uses a traffic light system: green (well-controlled), yellow (caution), and red (medical emergency). Monitoring symptoms and PEFR helps patients identify early deterioration.
Education is a critical component. Patients should be taught correct inhaler technique, the importance of adherence, and how to avoid asthma triggers such as tobacco smoke, allergens, respiratory infections, and environmental pollutants.
Pharmacological Management – Balancing Safety and Efficacy
Treatment of asthma in pregnancy follows a stepwise approach similar to non-pregnant adults, but with special attention to fetal safety.
1. Mild Intermittent Asthma: Short-acting beta-agonists (SABAs), particularly inhaled albuterol (salbutamol), are the first-line rescue medication. They are safe and effective, with minimal systemic absorption, making them compatible with pregnancy.
2. Mild Persistent Asthma: Inhaled corticosteroids (ICS) such as budesonide are preferred as first-line controller therapy. Budesonide has the most extensive safety data in pregnancy and is categorized as FDA Pregnancy Category B. Other ICS like fluticasone and beclomethasone are also considered safe but have less robust evidence.
3. Moderate Persistent Asthma: For patients requiring additional control, combination therapy with ICS and long-acting beta-agonists (LABAs), such as budesonide-formoterol, is recommended. The use of LABAs should always be in combination with ICS to reduce the risk of severe exacerbations.
4. Severe Persistent Asthma: In refractory cases, add-on therapies such as leukotriene receptor antagonists (e.g., montelukast), theophylline, or biologic agents may be considered. Montelukast is classified as Category B and may be used when benefits outweigh risks.
Systemic corticosteroids (e.g., prednisone) are used for acute exacerbations. While high-dose or prolonged use may be associated with gestational diabetes and preterm birth, short courses are generally safe and necessary to prevent hypoxemia.
All medications should be used at the lowest effective dose to maintain control.
Managing Asthma Exacerbations During Pregnancy
Acute asthma exacerbations require prompt treatment to prevent fetal hypoxia. Signs of an exacerbation include increased symptom frequency, decreased PEFR, or inability to speak in full sentences.
Management includes:
- Immediate use of SABA via inhaler or nebulizer.
- Repeat dosing every 20 minutes as needed.
- Administration of systemic corticosteroids (e.g., oral prednisone 40–60 mg daily for 5–7 days).
- Supplemental oxygen to maintain oxygen saturation ≥95%.
- Hospitalization for severe exacerbations with continuous monitoring of maternal and fetal status.
Fetal monitoring via cardiotocography (CTG) is recommended during severe attacks to detect signs of distress.
Monitoring Throughout Pregnancy and Delivery
Regular follow-up is essential, ideally every 4–6 weeks, with more frequent visits if asthma is unstable. Pulmonary function tests should be repeated periodically, and fetal growth should be monitored via ultrasound, especially in women with moderate to severe asthma.
During labor and delivery, most women with well-controlled asthma do not experience complications. Continuing routine asthma medications is critical. Epidural analgesia is safe and may reduce the work of breathing. Vaginal delivery is preferred unless obstetric indications require cesarean section.
Postpartum, asthma typically returns to pre-pregnancy status. Breastfeeding is strongly encouraged, as most asthma medications, including ICS and SABAs, are compatible with lactation.
Patient Education and Shared Decision-Making
Empowering patients with knowledge is key to successful asthma management. Healthcare providers should engage in shared decision-making, addressing concerns about medication safety, emphasizing that uncontrolled asthma is far riskier than treatment.
Topics for education include:
- Importance of medication adherence.
- Recognition of exacerbation signs.
- Avoidance of triggers.
- Smoking cessation support.
- Vaccination (e.g., influenza and pertussis vaccines are recommended during pregnancy).
Conclusion
Asthma in pregnancy requires a proactive, multidisciplinary approach involving obstetricians, pulmonologists, allergists, and primary care providers. By understanding the disease’s pathophysiology, implementing accurate diagnosis, following evidence-based treatment protocols, and involving patients in care planning, healthcare professionals can significantly improve outcomes. The overarching goal is to maintain optimal asthma control throughout pregnancy, thereby protecting both mother and baby. With proper management, the vast majority of women with asthma experience healthy pregnancies and deliver healthy infants.
References
- Schatz M, Dombrowski MP, Wise R, et al. Asthma in pregnancy: A practice parameter update 2020. Annals of Allergy, Asthma & Immunology. 2020;125(2):169-184. doi:10.1016/j.anai.2020.04.019
- National Asthma Education and Prevention Program (NAEPP). Guidelines for the Diagnosis and Management of Asthma (EPR-3). NIH Publication No. 08-5846. 2007.
- American College of Obstetricians and Gynecologists (ACOG). ACOG Practice Bulletin No. 90: Asthma in Pregnancy. Obstet Gynecol. 2008;111(2 Pt 1):457-464.
- Murphy VE, Namazy J, Schatz M, et al. Asthma during pregnancy: current mechanisms and future strategies for prevention. Lancet Respir Med. 2021;9(1):89-101. doi:10.1016/S2213-2600(20)30300-0
- FDA Drug Safety Communication: Update on asthma medicine safety during pregnancy. U.S. Food and Drug Administration. https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-update-asthma-medicine-safety-during-pregnancy
- Centers for Disease Control and Prevention (CDC). Managing Asthma During Pregnancy. https://www.cdc.gov/asthma/pregnancy.htm
