Asthma Medicines During Pregnancy

Asthma medicines in pregnancy are continued at usual doses because uncontrolled asthma, not asthma treatment, harms the foetus (hypoxia, preterm birth, low birth weight, pre-eclampsia). About one third of women improve, one third worsen and one third are unchanged; exacerbations peak at 24 to 36 weeks, often from viral infection or non-adherence.

Safety record. Inhaled corticosteroids, short- and long-acting beta-2 agonists and montelukast have reassuring data. Treat the oxygen saturation, not the fear of drugs.

Control target. Peak flow over 80% of best, daytime symptoms 2 days a week or fewer, no night waking, and no more than 2 doses of reliever a week.

Reliever. Salbutamol 100 micrograms for each actuation, 1 to 2 puffs (up to 4 puffs) by spacer as needed. Preferred in pregnancy where available: budesonide-formoterol 160/4.5 micrograms, 1 inhalation as needed (maximum 12 inhalations daily, 8 on regular maintenance).

Preventer. Inhaled corticosteroid at the lowest effective dose: budesonide 200 to 800 micrograms daily in 2 doses (preferred, most pregnancy data), or beclometasone 100 to 400 micrograms twice daily, or fluticasone 100 to 250 micrograms twice daily.

Add-on. Long-acting beta-2 agonist (formoterol or salmeterol) combined with the inhaled corticosteroid; montelukast 10 mg orally at night (continue if it controlled asthma before pregnancy); theophylline modified release 200 to 400 mg twice daily to a serum level of 5 to 12 mg/L (use with care; levels rise with infection and in late pregnancy).

Oral corticosteroid for exacerbation. Prednisolone 40 to 50 mg orally once daily for 5 to 7 days, no taper needed. Courses over 3 weeks warrant taper and glucose monitoring.

Acute severe asthma.

• Oxygen to keep saturation at 95% or more, to protect the foetus.
• Salbutamol 5 mg nebulised, repeat every 20 minutes for 3 doses, then every 1 to 4 hours (or 4 to 10 puffs by spacer every 20 minutes for 1 hour).
• Ipratropium bromide 500 micrograms nebulised every 20 minutes for 3 doses.
• Prednisolone 40 to 50 mg orally, or hydrocortisone 100 mg IV every 6 hours.
• Magnesium sulphate 2 g IV over 20 minutes for severe or life-threatening asthma.
• Intubation criteria match those for non-pregnant adults; consider early birth in late pregnancy if the mother deteriorates.

Severe asthma. Omalizumab or mepolizumab may continue if benefit is clear; start no new biologic in pregnancy except after specialist review.

Labour. Continue inhalers; give hydrocortisone 100 mg IV every 6 to 8 hours if prednisolone 5 mg or more has been taken for over 2 weeks in the past 3 months. Avoid carboprost (bronchospasm); use oxytocin, with ergometrine used cautiously. Use NSAIDs for analgesia only if the patient has tolerated them before.

Avoid. Non-selective and cardioselective beta-blockers (including labetalol in poorly controlled asthma), carboprost, aspirin and NSAIDs in aspirin-sensitive asthma (low-dose aspirin for pre-eclampsia prevention needs specialist review in that group), pseudoephedrine in the first trimester, systemic adrenaline except in anaphylaxis.

Adverse effects. Oral thrush and hoarseness with inhaled corticosteroid (rinse mouth, use spacer); tremor, palpitations and hypokalaemia with high-dose salbutamol; theophylline toxicity with nausea, tachycardia and seizures over 15 mg/L.

Interactions. Theophylline with ciprofloxacin, macrolides or cimetidine: toxicity. Rifampicin and carbamazepine lower theophylline and corticosteroid levels. Beta-2 agonists with corticosteroids and diuretics: hypokalaemia.

Special groups.

• Smokers and passive smokers: advise cessation and smoke-free homes.
• Kidney impairment: no adjustment of inhaled therapy.
• Liver impairment: reduce theophylline.
• Breastfeeding: all inhaled agents, montelukast, prednisolone and theophylline (infant irritability) are compatible.
• Regional: cooking smoke, kerosene and charcoal indoors are common triggers; advise clean fuels and ventilation. Salbutamol and beclometasone inhalers are widely available; spacers can be made from a 500 mL plastic bottle where commercial devices are scarce.

Monitoring. Peak flow twice daily with a written action plan, symptom review each visit, inhaler technique check at each visit, and monthly review in the second and third trimesters in moderate to severe asthma. Foetal growth scans at 32 and 36 weeks in severe asthma or after oral corticosteroid courses.

Adjustment. Step up if symptoms or reliever use occur more than twice a week; step down only after 3 months of stability and not in the first or third trimester.

Stopping rules. Do not stop inhaled corticosteroid because of pregnancy. Stop theophylline at the first sign of toxicity.

Referral and escalation. Refer to respiratory and obstetric medicine for severe asthma, oral corticosteroid dependence or any hospitalisation. Treat peak flow under 50% of best, inability to speak in sentences, saturation under 94%, or a silent chest as life threatening and escalate to critical care at once.