Asthma and respiratory disease in pregnancy

It is 26 weeks and the woman in front of you has had asthma since childhood. She stopped her beclometasone inhaler at the positive pregnancy test because her GP said "let's minimise medications in pregnancy". She now wheezes on the exam couch, her peak flow is 380 (best 520), and her CTG shows a baseline of 165 with reduced variability. The single biggest preventable cause of asthma exacerbation in pregnancy is the ICS that was never started — or that was stopped. This topic is the ICS that should not have been stopped.^[1][4]

Overview and definition

Asthma is chronic Th2-mediated airway inflammation with bronchial hyper-responsiveness and reversible airflow obstruction. In pregnancy the trajectory is unpredictable and the disease can worsen, improve or stay the same — but the treatment principle is unambiguous: control the inflammation to protect the fetus.^[6][7]

The pregnancy effect on asthma trajectory:^[8][10]

• About one-third of women improve in pregnancy (progesterone-mediated smooth muscle relaxation).
• About one-third worsen (especially with viral infections, in the late second trimester).
• About one-third stay the same.^[8][10]

The risk peaks where control was already poor at conception: uncontrolled asthma at booking predicts exacerbation, admission and adverse fetal outcome.^[1][11]

The physiological interaction with pregnancy:^[8]

• The diaphragm elevates and functional residual capacity falls by around 20% — there is less reserve.
• Tidal volume rises by progesterone-driven hyperventilation; PaCO2 falls to 28-32 mmHg in normal pregnancy.
• A pregnant asthmatic with a PaCO2 of 42 is no longer compensating — she is tired.^[8]

^{[1] [2] [3] [4]}

References12ShowHide

1. [1]Murphy VE, Clifton VL, Gibson PG Asthma exacerbations during pregnancy: incidence and association with adverse pregnancy outcomes Thorax, 2006.PMID 16443708
2. [2]Murphy VE, Wang G, Namazy JA, Powell H, Gibson PG, Chambers C, Schatz M The risk of congenital malformations, perinatal mortality and neonatal hospitalisation among pregnant women with asthma: a systematic review and meta-analysis BJOG, 2013.PMID 23530780
3. [3]Mirzakhani H, Carey VJ, McElrath TF, Laranjo N, O'Connor G, Iverson RE, Lee-Parritz A, Strunk RC, Bacharier LB, Macones GA, Zeiger RS, Schatz M, Hollis BW, Litonjua AA, Weiss ST The Association of Maternal Asthma and Early Pregnancy Vitamin D with Risk of Preeclampsia: An Observation From Vitamin D Antenatal Asthma Reduction Trial (VDAART) J Allergy Clin Immunol Pract, 2018.PMID 28923490
4. [4]Robijn AL, Jensen ME, McLaughlin K, Gibson PG, Murphy VE Inhaled corticosteroid use during pregnancy among women with asthma: A systematic review and meta-analysis Clin Exp Allergy, 2019.PMID 31357230
5. [5]National Asthma Education and Prevention Program Asthma and Pregnancy Working Group; National Heart, Lung, and Blood Institute NAEPP expert panel report. Managing asthma during pregnancy: recommendations for pharmacologic treatment-2004 update J Allergy Clin Immunol, 2005.PMID 15637545
6. [6]Davis AE, Wechsler ME, Namazy JA, Schatz M The safety of asthma treatment and management strategies in pregnancy Expert Rev Respir Med, 2025.PMID 40536883
7. [7]Namazy JA, Schatz M, Dombrowski M Clinical Updates in Women's Health Care Summary: Asthma Obstet Gynecol, 2018.PMID 29683908
8. [8]Murphy VE, Gibson PG Asthma in pregnancy Clin Chest Med, 2011.PMID 21277452
9. [9]Litonjua AA, Carey VJ, Laranjo N, Harshfield BJ, McElrath TF, O'Connor GT, Sandel M, Iverson RE Jr, Lee-Paritz A, Strunk RC, Bacharier LB, Macones GA, Zeiger RS, Schatz M, Hollis BW, Hornsby E, Hawrylowicz C, Wu AC, Weiss ST Effect of Prenatal Supplementation With Vitamin D on Asthma or Recurrent Wheezing in Offspring by Age 3 Years: The VDAART Randomized Clinical Trial JAMA, 2016.PMID 26813209
10. [10]Belanger K, Hellenbrand ME, Holford TR, Bracken M Effect of pregnancy on maternal asthma symptoms and medication use Obstet Gynecol, 2010.PMID 20177287
11. [11]Namazy JA, Murphy VE, Powell H, Gibson PG, Chambers C, Schatz M Effects of asthma severity, exacerbations and oral corticosteroids on perinatal outcomes Eur Respir J, 2013.PMID 22903964
12. [12]Namazy JA, Schatz M Chronic Management of Asthma During Pregnancy Immunol Allergy Clin North Am, 2023.PMID 36411009