Asthma During Pregnancy

Contributor: D Pasko, MD                                                                                                      Last Update: June 2020

Background:

• Incidence – 4 to 8% of pregnancies.
• Course of disease variable with up to 1/3 of women experiencing worsening symptoms.
• Potential complications – decreased fetal oxygenation, preterm delivery, fetal growth restriction, and preeclampsia.

Diagnosis:

• Suspected based on a history of episodic wheeze, cough, and dyspnea with classic exam findings of wheezing, tachypnea, prolonged expiratory phase.
• Formal diagnostic criterion: reversible airway obstruction on spirometry following bronchodilator administration; however, a history of classic asthma symptoms with response to bronchodilator therapy may be utilized to diagnose asthma in pregnancy.
• Differential diagnosis: dyspnea of pregnancy, GERD, bronchitis, and chronic cough.
• Referral to pulmonologist/allergist should be considered if uncertain diagnosis or need for formal pulmonary function testing or allergy component.

Management:

• Initial exam – Obtain history of prior disease course (hospital visits, mechanical ventilation, oral corticosteroid use, asthma flares in prior pregnancies, medication use, and noncompliance) as well as assessment of comorbidities and allergy history. Classify disease severity based on symptom burden and pulmonary function (peak expiratory flow rate, PEFR) or forced expiratory volume in the first second of expiration (FEV1).  See Table 1 and Figure 1 for overview.

Effective management of asthma in pregnancy is founded on 4 critical components:

1. Step care therapy – Utilize the lowest amount of pharmacotherapy necessary to prevent episodic maternal hypoxia (Table 1). At each visit, evaluate the need to change asthma severity classification based on current disease control.  Decisions regarding pharmacotherapy should be guided by asthma classification.  Evaluate medication compliance, unscheduled clinic visits, and/or a history of hospital visits.
2. Objective lung function assessment – A baseline PEFR should be established for all asthmatics to permit objective comparison later in pregnancy (average PEFR for reproductive age woman is approximately 400L/min; patient instructions provided below). The PEFR should be regularly assessed for patients with persistent asthma.  Women with moderate or severe persistent asthma should be encouraged to monitor their PEFR daily with an asthma diary.
3. Avoidance of environmental triggers such as tobacco smoke and management of comorbidities including rhinitis and GERD.
4. Individualized patient education – Discuss appropriate technique for inhaler administration and provision of an asthma action plan highlighting their peak flow ranges, medications and dosages (accessible at http://www.nhlbi.nih.gov/health/public/lung/asthma/asthma_actplan.pdf)

Medication

• Albuterol is the preferred rescue therapy for asthma management.
• Budesonide or an equivalent inhaled corticosteroid is the preferred first-line controller therapy for persistent asthmatics.
• Salmeterol is the preferred long-acting beta agonist for add-on therapy when a medium dose inhaled corticosteroid provides insufficient treatment. An inhaled long-acting beta agonist should not be prescribed in isolation without an inhaled corticosteroid due to an association with asthma related death.
• Theophylline or Montelukast represent alternate add-on therapies for any of the levels of persistent asthma.

When adding a new agent allow a one-month trial and continue the new medication only if there is sufficient improvement in symptoms or lung function.

Table 2 provides examples of South Carolina Medicaid formulary options for various asthma therapies (current as of 6/2020). If prescribing a medication other than albuterol for asthma therapy, it is recommended to reference the patient’s insurance formulary (e.g., Google search for South Carolina Medicaid Healthy Choices formulary) to prevent delays in medication initiation related to insurance coverage.

Management of Acute Asthma Exacerbation in Pregnancy

Initial Evaluation and Management:

• History and physical
• Patient in seated position rather than supine
• O2 sat on room air
• Peak Expiratory Flow Rate (PEFR)
• Maintain O2 sat > 95%
• Fetal monitoring and/or BPP (viable fetus)
• Intravenous fluid containing glucose at a rate of at least 100 ml/hr
• Chest radiograph
• Arterial blood gas (respiratory distress, tachypnea, SaO2 <95%, PEFR <50%)

Poor Prognosticators: 

• PEFR < 50% of predicted
• Arterial pH <7.35
• PaCO2 > 42 mmHg
• PaO2 <70 mmHg
• Confusion, distress

Pharmacologic Management:

• Beta-agonist bronchodilator (metered-dose inhaler or nebulizer) up to 3 doses in first 60 minutes
• Nebulized ipratropium (Atrovent)
• Intravenous methylprednisolone (with initial therapy in patients on regular corticosteroids or with poor response during the first hour of treatment) 60mg every 6-12 hours for 48 hours.  Taper as patient improves.
• Consider IV magnesium sulfate 2 grams infused over 20 minutes (not for routine use, life-threatening exacerbations in conjunction with corticosteroids).
• Consider subcutaneous terbutaline 0.25 mg if patient not responding to the above therapy.

Labor and Delivery Management of Asthmatics:

• Continue asthma medications
• Consider PEFR on admission and q 12 hours if acute exacerbation
• Avoid dehydration
• Provide adequate analgesia
  • Epidural anesthesia is encouraged
  • Fentanyl is the preferred intravenous narcotic
  • Ketamine and halogenated anesthetics are the preferred general anesthetics
• Prevent adrenal crisis (stress dose steroids for patients on chronic oral steroids)
• Postpone elective delivery during asthma exacerbation
• Occasionally delivery may improve unstable asthma
• Cervical ripening – PGE1 or E2
• Avoid indomethacin, labetalol, hemabate and methergine.
• Magnesium sulfate or calcium channel blocker for tocolysis

Peak Flow Meter Instructions

• Move peak flow meter indicator to 0.
• Stand up straight.
• Take a deep breath and fill lungs completely.
•  Hold breath, place mouthpiece between teeth and close lips around meter.
• Blow out air as hard and fast as possible in a single blow.
• Record the PEFR number.
• Repeat above steps two additional times; the highest of the 3 readings is the PEFR.

Asthma Action Plan and How to Control Things That Make Your Asthma Worse

Click on link: https://www.nhlbi.nih.gov/health/public/lung/asthma/asthma_actplan.pdf

---

References

1. National Heart Lung and Blood Institute Guidelines for the Diagnosis and Treatment of Asthma. www.nhlbi.nih.gov/guidelines/asthma. Accessed May 30, 2020.
2. Asthma in pregnancy. ACOG Practice Bulletin No. 90. American College of Obstetricians and Gynecologists. Obstet Gynecol 2008; 111:457–64.
3. Dombrowski MP.  Asthma and pregnancy.  Obstet Gynecol 2006;108:667-81.
4. Bonham CA. Asthma Outcomes and Management During Pregnancy. Chest 2019; 153(2):515-527.