What is the best approach to manage asthma in a pregnant patient?

Management of Asthma in Pregnancy

Continue all asthma medications during pregnancy, as uncontrolled asthma poses far greater risks to both mother and fetus than the medications used to treat it. 1, 2

Core Management Principles

Primary Treatment Goal

• Maintain optimal asthma control to prevent maternal hypoxia and ensure adequate fetal oxygenation 1, 3
• Uncontrolled asthma increases risks of perinatal mortality, preeclampsia, preterm birth, low birth weight, and intrauterine growth restriction 1, 3, 4
• The risks from uncontrolled asthma substantially exceed any theoretical medication risks 2, 5

Monthly Monitoring Requirements

• Evaluate asthma symptoms and pulmonary function (spirometry or peak expiratory flow) at every prenatal visit 1, 2, 5
• Asthma course changes in approximately two-thirds of pregnant women—one-third improve, one-third worsen, and one-third remain stable 1, 5
• Exacerbations most commonly occur during the second and third trimesters, with relative stability in the first trimester and last month 1
• Involve obstetrical care provider in assessment and monitoring throughout pregnancy 2

Stepwise Pharmacologic Management

Quick-Relief Medications (All Severity Levels)

Albuterol (salbutamol) is the preferred short-acting beta-agonist due to the most extensive safety data from 6,667 pregnant women, including 1,929 with asthma 1, 2, 6, 5

Dosing for symptom relief:

• 2-4 puffs via metered-dose inhaler as needed for acute symptoms 1, 6
• Up to 3 treatments at 20-minute intervals or single nebulizer treatment (2.5 mg) for acute exacerbations 1, 2

Critical warning sign: If albuterol is needed more than twice weekly in intermittent asthma, or if use is increasing in persistent asthma, this signals inadequate control requiring initiation or intensification of inhaled corticosteroids 1, 2, 5

Long-Term Controller Medications

Inhaled corticosteroids are the preferred maintenance therapy for all levels of persistent asthma 1, 5, 3

Budesonide is the first-choice inhaled corticosteroid because it has:

• The most extensive pregnancy safety data 1, 2, 5
• FDA/Australian TGA Category B classification 7
• Reassuring evidence from large Swedish registry studies of 2,534 pregnant women showing no increased risk of congenital malformations (3.6% vs 3.5% general population rate) 7
• No increased risk of orofacial clefts (4 observed vs 3.3 expected) 7

Dosing ranges for budesonide (dry powder inhaler): 1

• Low dose: 200-600 mcg daily
• Medium dose: 600-1,200 mcg daily
• High dose: >1,200 mcg daily

Other inhaled corticosteroids are acceptable alternatives if the patient was well-controlled on them pre-pregnancy, though budesonide has superior safety data 1

Add-On Therapies for Inadequate Control

Long-acting beta-agonists (LABAs): Can be added to inhaled corticosteroids for persistent symptoms, though pregnancy data are more limited than for short-acting agents 1

Leukotriene receptor antagonists (montelukast, zafirlukast): Minimal human pregnancy data available, though animal studies are reassuring 1, 2

• Consider only when inhaled corticosteroids plus LABAs provide inadequate control
• Do not use zileuton (5-lipoxygenase inhibitor) due to lack of safety data 1

Management of Acute Exacerbations

Home Treatment Protocol

For moderate exacerbations: 2, 6

• Albuterol 2.5 mg via nebulizer every 20 minutes for 3 doses, then every 1-4 hours as needed
• OR 4-8 puffs via MDI with spacer every 20 minutes for 3 doses, then every 1-4 hours

For severe exacerbations requiring emergency care: 2

• Combination nebulizer: 2.5 mg albuterol + 0.5 mg ipratropium every 20 minutes for 3 doses, then every 2-4 hours
• Systemic corticosteroids: Prednisone 40-60 mg daily for 3-10 days (outpatient) or 120-180 mg/day in divided doses for 48 hours, then 60-80 mg/day until peak flow reaches 70% predicted (inpatient) 2

Hospital Management

Aggressive treatment is essential as inadequate control poses greater risk than medications 2

Monitoring requirements: 2

• Maintain maternal oxygen saturation >95% for fetal well-being
• Consider arterial blood gas in severe cases to assess maternal and fetal oxygenation
• Monitor for maternal tachycardia, hyperglycemia, and hypokalemia with beta-agonist use
• Fetal heart rate monitoring if maternal tachycardia develops

Obstetrical involvement: Notify obstetrical team for assessment and fetal monitoring 2

Fetal Surveillance

For moderate to severe or suboptimally controlled asthma: 2

• Serial ultrasounds starting at 32 weeks gestation to assess fetal growth
• Consider antenatal fetal well-being testing

For well-controlled mild asthma: Routine obstetrical care is appropriate 3

Common Pitfalls to Avoid

Medication Discontinuation

Never reduce or discontinue asthma medications due to pregnancy concerns 2, 5, 8

• This is the most dangerous error in asthma management during pregnancy
• Uncontrolled asthma causes fetal hypoxia, which is far more harmful than medication exposure 1, 3
• Many exacerbations are precipitated by patient or provider fear of medication teratogenicity 8, 9

Inadequate Treatment Escalation

• Using approximately one canister of albuterol per month indicates poor control even if not using it daily 1
• This signals need for controller therapy intensification, not continued reliance on rescue medication 1, 5

Medication Selection Errors

• Avoid oral decongestants in early pregnancy due to potential association with rare birth defects 2
• Do not use systemic epinephrine for exacerbations due to teratogenic effects and placental vasoconstriction 10
• Avoid glycopyrronium nebulization due to lack of pregnancy safety data; use ipratropium instead 2

Monitoring Failures

• Failure to perform monthly pulmonary function assessments misses deterioration in two-thirds of patients whose asthma course changes 1, 5
• Lack of multidisciplinary coordination between respiratory specialist, obstetrician, and general practitioner compromises care 1, 8

Labor, Delivery, and Postpartum

Continue all asthma medications during labor and delivery 1, 3

Breastfeeding is strongly encouraged as it may protect infants from developing allergies when breastfed for at least 4 months 1, 3

Postpartum management: Review treatment every 3-6 months and consider gradual stepwise reduction if control is maintained 1

Special Considerations

Vitamin D Supplementation

• Most pregnant women with asthma have vitamin D levels <75 nmol/L, which are associated with increased risk of childhood asthma in offspring 1
• Adequate vitamin D during pregnancy influences neonatal immune system development and may protect against asthma-related outcomes 1

Exercise During Pregnancy

• Maternal exercise reduces incidence of low fetal birthweight and is particularly important for overweight or obese women with asthma 1
• Overweight/obese women with asthma have twice the frequency of exacerbations during pregnancy 1