Basics
Description
Chronic inflammatory disease of the airway characterized by:
- Reversible airway obstruction
- Heightened airway reactivity to various stimuli
Epidemiology
Incidence
- Asthma affects between 3.7% and 8.4% of pregnant women and is the most common chronic respiratory disease affecting pregnant women.
- During pregnancy, ¢ ¼5.8% of women hospitalized with asthma exacerbation.
Prevalence
In the US, increasing prevalence in women of childbearing age from ¢ ¼3% to >8% since 1994.
Risk Factors
- Risk factors for exacerbations in pregnancy:
- Baseline asthma severity as defined by recommendations of National Asthma Education and Prevention Program (NAEPP) working group on asthma in pregnancy
- Viral infections are an important trigger.
- Lack of appropriate treatment with inhaled corticosteroids
- Noncompliance with asthma medication
- Asthma exacerbations most frequent between 17 and 36 weeks gestational age with improvement in symptoms in last month of pregnancy.
General Prevention
- Patients with well-controlled asthma can have excellent pregnancy outcomes.
- Suboptimal control during pregnancy may be associated with increased maternal or fetal risk.
- Avoidance or control of asthma triggers
- 73 " 85% of patients have positive skin tests to common allergens including animal dander, house dust mites, pollens, molds.
- Other triggers to avoid: Tobacco smoke, strong odors, air pollutants, food additives, medications including aspirin
- Exercise-induced asthma can be avoided with inhalation of albuterol 30 minutes before exercise.
Pathophysiology
Same as in the nonpregnant patient; however, there are some physiological changes that occur to the respiratory system during pregnancy:
- Hormonally mediated increase in minute ventilation with increase in tidal volume
- Respiratory rate is relatively unchanged.
- Compensated respiratory alkalosis with normal PaCO2 = 28 " 32 mm Hg; pH = 7.40 " 7.45
- Increase in pH secondary to respiratory alkalosis is blunted by an increase in renal excretion of bicarbonate.
- Mild increase in PaO2 up to 110 mm Hg
- Structural changes to chest wall result in decrease in functional residual capacity.
- Flow rates are relatively unchanged.
Etiology
Same as in the nonpregnant population
Associated Conditions
- Gastroesophageal reflux
- Postnasal drip
- Rhinitis
Diagnosis
History
- Characteristic symptoms of wheezing, cough, shortness of breath, chest tightness
- Symptoms may be worse at night.
- Triggers = allergens, infections, and exercise
- Symptoms worsened by gastroesophageal reflux disease (GERD), rhinitis, sinusitis, gestational rhinitis
- Identify patients at risk for fatal asthma
- History of intubations
- Frequent emergency room visits
- Large fluctuations in peak flow
- Significant reversibility
Physical Exam
- Pulse oximetry to measure oxygenation
- Use of accessory muscles
- Ability to speak in full sentences
- Wheezing on auscultation
- Examine patient (especially if in distress) either seated or supine, with lateral tilt to pelvis, to prevent inferior vena cava (IVC) compression by uterus which causes reduction in venous return.
Tests
Lab
Initial Labs
ABG if oxygenation <95% or significantly reduced peak flow
Follow-up
Normal PaCO2 in pregnant women may mean impending respiratory failure.
Imaging
- If clinically suspected:
- Chest x-ray to rule out pneumonia
- CT angiogram of chest or V/Q scan to rule out pulmonary embolism
- <5 rads of ionizing radiation exposure during pregnancy not thought to increase risk for congenital malformations, growth restriction, or miscarriage.
- Chest x-ray: <0.005 rads
- Chest CT: <0.03 rads
- V/Q scan: <0.06 rads
Surgery
- Pulmonary function tests
- FEV1 and peak expiratory flow rate
Pathological Findings
Same as in nonpregnant population
Differential Diagnosis
- Dyspnea of pregnancy
- GERD
- Chronic cough from postnasal drip
- Bronchitis
- Pulmonary edema
- Pulmonary embolism
- Amniotic fluid embolism
- Cardiomyopathy
- Foreign body/upper airway obstruction
- Vocal cord dysfunction
Treatment
Medication
First Line
Budesonide, beclomethasone, and albuterol with most safety data in pregnancy
Second Line
- Long-acting ²-agonists (salmeterol/formoterol)
- Cromolyn, leukotriene receptor antagonists, and theophylline are alternatives but not preferred treatments.
- Systemic steroids in severe exacerbations
- Safety data on monoclonal antibodies, such as omalizumab, are lacking in pregnancy, despite an FDA category B rating.
Additional Treatment
General Measures
- Goal to control asthma for maternal health, quality of life, and normal fetal maturation
- Risk of uncontrolled asthma outweighs risk of medications used to treat disease.
- Asthma management during pregnancy:
- Assess and monitor including measuring pulmonary function (1)[B]
- Control factors contributing to asthma severity
- Patient education (1)[A]
- Develop asthma management plan that patient can follow during exacerbations (1)[B]
- Stepwise approach for managing asthma based on NAEPP guidelines 2004 update
Mild intermittent asthma:
- Short-acting bronchodilators for quick relief of symptoms as needed (1)[A]
- Albuterol preferred agent as most safety data (2)
Mild persistent asthma:
- Daily low-dose inhaled corticosteroid (1)[A]
- Budesonide is preferred inhaled steroid as no adverse outcomes during pregnancy (2)[B].
- Beclomethasone also safe in pregnancy; however, if requiring high doses of inhaled steroids, more safety data with budesonide.
- No data indicate that other inhaled corticosteroids unsafe in pregnancy. Therefore, other inhaled corticosteroids may be used during pregnancy if used prior to pregnancy.
Moderate persistent asthma:
- Combination of low-dose inhaled corticosteroid and long-acting ²-agonist OR increase dose of inhaled steroid to medium-dose range
- Long-acting ²-agonists (1)[A]
- Safety profile similar to albuterol
- Salmeterol preferred over formoterol
Severe persistent asthma:
- Increase dose of inhaled corticosteroid to high-dose range
- If this is insufficient, add oral steroid (1)[A]
- Although oral steroids carry some risk during pregnancy, benefit of treating with steroids by far outweigh their risks.
Issues for Referral
- Patients with moderate-to-severe asthma may be at risk for pregnancy complications.
- Scheduling of prenatal appointments should be based on clinical judgment.
- Monthly or more frequent evaluations of asthma symptoms and pulmonary function
In-Patient Considerations
Initial-Stabilization
Asthma exacerbation
- Assess severity:
- Ability to speak in full sentences
- Accessory muscle use and suprasternal retractions
- Note presence of fetal activity and monitor fetus
- Peak expiratory flow <50% of personal best or predicted suggests severe exacerbation
- Prevent maternal hypoxia, hypercarbia, reversal of bronchospasm, and exhaustion
- PaCO2 >35 mm Hg in mother may imply impending respiratory failure. Fetal hypoxemia and acidosis can occur even though maternal hypoxemia is absent.
- Oxygen supplementation to prevent fetal hypoxemia while observing mother for hypercapnia
- Fluid status should be assessed carefully and IV fluid hydration administered as necessary to help with placental perfusion.
Initial treatment
- Short-acting inhaled ²-agonist: 2 " 4 puffs at 20 minute intervals 3 or a single nebulizer treatment
- Ipratropium bromide (500 ¼g) in severe cases for synergistic effect
- Systemic steroids indicated if no improvement of symptoms or peak flows with initial bronchodilator treatment and if moderate or severe exacerbation
Management of acute asthma during labor and delivery
- All regularly scheduled medications should be continued during labor and delivery.
- Stress doses of steroids (e.g., hydrocortisone 100 mg) q8h from onset of labor until 24 hours postpartum in patients treated with systemic steroids chronically or with numerous short courses of steroids during pregnancy
- Avoid morphine and meperidine as they may cause histamine release
- If tocolytic therapy is considered for preterm labor, avoid indomethacin as it may induce bronchospasm in aspirin-sensitive asthmatics. Consider using magnesium sulfate or terbutaline instead in consultation with obstetric team.
- Avoid systemic ²-agonists as systemic + inhaled ²-agonists may cause significant adverse effects.
Admission Criteria
- Decision to hospitalize patient or to discharge home is based on response to treatment in first 4 hours in the emergency room.
- Would consider hospitalization in patients with new onset asthma who need significant teaching or have poor social support, or those with worsening symptoms on systemic steroids.
Nursing
- Asthma education and patient involvement in own care are crucial to good asthma management (1)[A].
- Nursing staff can help with education of patient about disease, inhaler technique, symptom monitoring, trigger and allergen recognition and avoidance.
Discharge Criteria
- Adequate control of symptoms with return to near baseline peak flows
- Prior to discharge, review asthma education and asthma exacerbation plan with patient.
Ongoing Care
Follow-Up Recommendations
Patient Monitoring
- Close medical follow-up
- At initial visit, perform baseline spirometry and monitor at follow-up visits.
- Patients to monitor peak flows at home and to use them as part of outpatient asthma care plan.
- Consider serial fetal ultrasounds starting at 32 weeks for patients with suboptimally controlled or moderate-to-severe asthma.
Patient Education
Educate patients on rescue management and recognition of symptoms of early exacerbation
Prognosis
- Women with well-controlled asthma generally have good pregnancy outcomes.
- Uncontrolled asthma may increase risk of perinatal outcomes.
- Less frequent exacerbations in patients whose asthma remains mild in pregnancy but exacerbations increase with increase in asthma severity.
Complications
- Asthma exacerbations during pregnancy are associated with low birth weight babies.
- Increased risk of congenital malformations in women with a history of severe asthma.
References
1 NAEPP Expert Panel Report 3: Guidelines for the diagnosis and management of asthma, 2007. Available at http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf2 Managing asthma during pregnancy: Recommendations for pharmacologic treatment 2004 update. J Allergy Clin Immunol. 2005;115:34 " 46.
Additional Reading
1 Asthma in pregnancy. ACOG practice bulletin no. 90. Obstet Gynecol. 2008;111:457 " 464. [View Abstract]2Bracken MB, Triche EW, Belanger K. Asthma symptoms, severity, and drug therapy: A prospective study of effects on 2205 pregnancies. Obstet Gynecol. 2003;104:739 " 752. [View Abstract]3Cousins L. Fetal oxygenation, assessment of fetal wellbeing, and obstetric management of the pregnant patient with asthma. J Allergy Clin Immunol. 1999;103(Suppl):S343 " S349. [View Abstract]4Dombrowski MP, Schatz M. Asthma in pregnancy. Clin Obstet Gynecol. 2010;53(2):301 " 310. [View Abstract]5Murphy VE, Clifton VL, Gibson PG. Asthma exacerbations during pregnancy: Incidence and associations with adverse pregnancy outcomes. Thorax. 2006;61:169 " 176. [View Abstract]6Murphy VE, Gibson PG. Asthma in pregnancy. Clin Chest Med. 2011;32:93 " 110. [View Abstract]7Murphy VE, Gibson PG, Clifton VL. Asthma during pregnancy: Mechanisms and treatment implications. Eur Resp J. 2005;25:731 " 750. [View Abstract]8Schatz M, Dombrowski MP. Asthma in pregnancy. N Engl J Med. 2009;360:1862 " 1869. [View Abstract]
Additional-Reading-See-Also
- Classification of asthma severity and control in pregnant patients " ACOG Practice Guideline Asthma in Pregnancy
- Step Therapy Medical Management of Asthma during Pregnancy " ACOG Practice Guidelines
Codes
ICD9
- 493.90 Asthma, unspecified type, unspecified
- 648.90 Other current conditions classifiable elsewhere of mother, unspecified as to episode of care or not applicable
ICD10
- O99.511 Diseases of the resp sys comp pregnancy, first trimester
- O99.512 Diseases of the resp sys comp pregnancy, second trimester
- O99.519 Diseases of the resp sys comp pregnancy, unsp trimester
- O99.513 Diseases of the resp sys comp pregnancy, third trimester
- J45.909 Unspecified asthma, uncomplicated
SNOMED
- 199293005 diseases of the respiratory system complicating pregnancy, childbirth and the puerperium (disorder)
- 195967001 asthma (disorder)
Clinical Pearls
- It is safer for pregnant women with asthma to be treated with asthma medications than for them to have asthma symptoms or exacerbations.
- Inadequate control of asthma is a greater risk to the fetus than are asthma medications.
- The ultimate goal of asthma therapy in pregnancy is to maintain adequate control.