• Information
  1. Respiration in Pregnancy
  2. Effect of Asthma on Pregnancy
  3. Chronic Asthma Treatment in Pregnancy
  4. Acute Therapy
• Resources

A. Respiration in Pregnancy

1. Tidal volume increase by 30-50%
2. Minute ventilation increased 10-20%
3. Oxygen consumption increased20%
4. CO2 production increased 30-40%
5. These changes are called "physiologic alkalosis of pregnancy"

B. Effect of Asthma on Pregnancy [2]

1. Overall good prognosis during pregnancy
2. Asthma Increases Maternal Complication Risks in Pregancy
   1. 3X risk for hyperemesis gravidarum
   2. 2X risk for uterine hemorrhage
   3. 2X risk for preeclampsia, placenta previa and C-section
3. Asthma (particularly severe) Increases risks to fetus
   1. Increased incidence of preterm births
   2. Intrauterine growth retardation (IUGR)
4. Pregnancy has no overall effect on asthma (33% worse, 33% no change, 33% better)
5. The critical issue is to maintain maternal (and therefore fetal) oxygen levels

C. Chronic Asthma Treatment in Pregnancy

1. Inhaled Bronchodilators
   1. Short-acting ß2-selective agonists preferred, such as albuterol
   2. Symptoms not controlled by 100µg albuterol/day - consider adding beclomethasone
   3. Terbutaline or epinephrine may also be used
   4. Long-acting ß2-agonists (salmeterol, formoterol) have not been studied carefully
2. Oral Glucocorticoids
   1. Beclomethasone inhaler (Vancenase®, Beconase®; 8-20 inhalations per day)
   2. Triamcinolone (Azmacort®) has been shown to be teratogenic in animals
   3. If high doses are required, consider adding long acting ß2-agonist or theophylline
3. Prednisone - up to 30-60mg po qam
4. Other Agents
   1. Cromylin Sodium - Nedocromil®
   2. Astemizole (Hismanal®) has been studied prospectively in pregnancy and is safe
   3. Tripelennamine (first generation antihistamine) demonstrated safe in human pregnancy
   4. Chlorpheniramine, diphenhydramine (Benadryl®), and hydroxyzine also appear to be safe
   5. Pseudoephedrine (Sudafed®) also appears to be safe in pregnancy
5. Theophylline - usually second line, but is safe in pregnancy
6. Antibiotics - penicillins, cephalosporins, erythromycin
7. Influenza Vaccination yearly
8. Immunotherapy can be continued through therapy
9. Remove as many asthma stimulants as possible - clean rugs, new mattresses
10. Goal is to minimize medications AND asthma attacks as much as possible

D. Acute Therapy

1. Inhaled ß2-agonist therapy
   1. High doses often required with high flow oxygen
   2. Subcutaneous terbutaline (0.25mg) is also acceptable
2. Epinephrine 0.3mL of 1:1000 solution q20 minutes
3. Glucocorticoids
   1. High dose intravenous methylprednisolone 80-125mg initial dose
   2. Oral taper
   3. Glucocorticoids are safe in pregnancy
4. Chest radiograph with abdominal shielding recommended to rule out pneumonia
5. Other Agents Safe in Pregnancy
   1. Theophylline
   2. Cromylin sodium
   3. Beclomethasone
   4. Penicillins, Cephalosporins
   5. Tripelennamine

Resources

Aa Gradient

References

1. Lemanske RF Jr and Busse WW. 1998. JAMA. 278(22):1855
2. Tan KS and Thomson NC. 2000. Am J Med. 109(9):727