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Asthma and Pregnancy 


The management of asthma in pregnancy may be a cause of heightened concern for healthcare professionals. During pregnancy, asthma control often changes due to mechanical and hormonal influences, though this can be unpredictable1. In general, one third gets better, one third worsens and one third stays the same during pregnancy. The course of asthma tends to be similar in successive pregnancies however this is not always the case2,3.

Studies have shown that 11–18% of pregnant women with asthma will have at least one emergency department visit for acute asthma. Exacerbations of asthma during pregnancy are more common in the second and third trimester and are less likely to occur in the last 4 weeks of pregnancy and this is thought to be likely due to the release of endogenous steroid3.

Clinical signs and symptoms

Pregnant asthmatics present with similar signs and symptoms as non-pregnant asthmatics. Common symptoms of poor asthma control in pregnancy are breathlessness, cough, wheeze, chest tightness, nocturnal cough4. When examining patients, they may have an increased respiratory rate, evidence of wheeze and tachycardia5.

When taking a history from the patient it’s important to assess for triggers such as:

Animal fur
Extreme temperatures
Medications (NSAIDs and beta blockers) 


Asthma is a clinical diagnosis. Signs and symptoms with appropriate objective tests will lead to a diagnosis. In pregnancy peak flows are a reliable diagnostic test and are non-invasive. 
A ≥ 20% diurnal variation in PEFR (peak expiratory flow rate) for 3 or more days per week during a 2 week period of monitoring is a diagnostic criteria.

There are physiological changes that occur in pregnancy which may impact on the tests that we may conduct6:

  • FEV1, FVC and peak expiratory flow rate (PEFR) don’t change significantly so can and should be used
  • Residual volume and forced residual capacity (FRC) fall along with total lung capacity (TLC) in the last trimester
  • Increased minute ventilation secondary to increased tidal volume
  • No increased respiratory rate
  • Compensatory respiratory alkalosis
  • Relative hypercapnia and higher PaO26

Poor asthma control and associations

There is some association between uncontrolled asthma and following conditions3:

1. Pregnancy induced hypertension & pre-eclampsia
2. Preterm births and preterm labour fetal growth restriction, neonatal morbidity (transient tachypnoea of new born, admission to neonatal unit, seizures). 

A common cause of deterioration in disease control in pregnancy for asthmatics is the reduction or even complete cessation of medication due to fears about its safety and risk to the baby1. Good management improves outcomes7:

  • Start prenatally: optimise meds, educate, support, continue in pregnancy
  • Aim to reduce exacerbations
  • Allay concerns about the medication risk as the benefits of good asthma control outweigh any potential medication risks
Peak Flow Meters are available to order from GSK's resources page here 

Poor adherence to medications

Pregnant women with asthma decrease medication use from 5-13 weeks
Gestation8. There has been published data and this is a reflection of both poor understanding around asthma in pregnancy from both patients and health care professional’s perspective. This study showed a:

• 23% reduction in inhaled corticosteroids

• 13% reduction in short-acting beta agonists

• 54% reduction in rescue steroids8 


Asthma control is the most important factor and good control outweighs any potential medication risk whether that is inhaler therapy or other standard treatments for asthma.
Inhaler should be used and titrated as per BTS/SIGN guidelines. Theophylline and steroids can be used as per non pregnant asthmatics, although BTS guidelines recommend checking Theophylline levels in pregnancy, as a lower therapeutic range may be appropriate9.

If patients are on montelukast and are well controlled, then this should be continued again based upon the benefit good asthma control and the risk of worsening control if this was stopped10. The treatment is exactly the same as non-pregnant asthmatics. If clinically indicated steroids should not be withheld9.

Steroids in pregnancy

Inhaled, oral, and IV steroids can all be used in pregnant asthmatics if clinically required. Only minimal amounts of inhaled dose are systemically absorbed. Prednisolone is metabolised by placenta and only 10% reaches the foetus. There were concerns previously about the risk of cleft lip and cleft palate with the use of steroids in the first trimester. However recent evidence shows there is no apparent increased risk9.

FeNO in pregnancy

Evidence lacking around the use of FENO in pregnancy.  FENO can be used in conjunction with clinical assessment. The 2 papers below show a slightly lower cut off for FENO pregnancy. More evidence is required to justify its use11,12.

Pre-pregnancy care


All professionals providing care for women of childbearing age including general practitioners and obstetricians should be aware that: 

Control of asthma should be optimised before conception9 

There is some evidence that the course of asthma is similar in successive pregnancies9

Women need to receive clear education that the risk of harm to the baby from severe or chronically undertreated asthma outweighs any small risk from the medications used to control asthma

Women should be assessed for inhaler technique. Technique with metered dose inhalers is often less than ideal and a spacer is strongly recommended4

Non-adherence with preventer therapy needs continuous assessment in women who remain poorly controlled13 

Women should be advised about the importance of getting the flu vaccination during pregnancy as early as possible in the flu season14 

Asthma control

Avoid known trigger factors2:

Reassure pregnant women to continue their asthma medications. This will improve treatment adherence for the duration of pregnancy 

Encourage personalised self-management plans9,15


If an acute severe attack occurs, then this should be treated as an emergency in hospital 
Serial growth scans should be performed in women with severe asthma from 28 weeks onwards 4 weekly and ideally should be under an asthma specialist in conjunction with an obstetrician. Early referral to the anaesthetic team should occur if asthma is severe or poorly controlled16.


Asthma attacks or exacerbations are exceedingly rare in labour due to endogenous steroids 

Women should not discontinue their inhalers during labour as there is no evidence to suggest that β2 agonist’s inhalers will impair uterine contractions. 

All analgesic options for pain relief can be used in asthma, but epidural analgesia may be particularly beneficial in cases where there is poor control or severe symptoms. In these cases this should be part of an MDT approach. 

Continuous fetal monitoring should be performed when asthma is uncontrolled or severe. Where possible, regional rather than general anaesthesia is preferable because of the decreased risk of bronchospasm, chest infection and post-operative atelectasis 

Caesarean section is reserved largely for obstetric indications. In certain situations where the asthma is severe a decision to perform a caesarean delivery may be made in close conjunction with the respiratory physician, to ensure a safe pre-term delivery. In majority cases the aim is for normal delivery6,16 


Most of the medications, including oral corticosteroids should be used in breast feeding mothers if clinically required, however, because it is not known whether azithromycin may have adverse effects on the breast-fed infant, nursing should be discontinued during treatment with azithromycin9,15,17

Take home points

Asthma treatment adherence reduces during pregnancy

Reassurance around compliance of medications is essential

All standard asthma medications should be used as the risk of poor asthma control outweighs the risk potential risk from medications to patient and the baby

More evidence is required around the use of FENO in pregnancy

Do not stop montelukast if they are already on treatment and are well controlled

Give steroids if clinically indicated


1. Global strategy for asthma management and prevention: 2019:1-201(v1.0) - Asthma control in pregnancy (p.80).
2. Michael Schatz, Kathy Harden et al. The course of asthma during pregnancy, post-partum, and with successive pregnancies: a prospective analysis. J Allergy Clin Immunol 1988; 81(3):509-17
3. BTS-SIGN. British guideline on the management of asthma. October 2016 
4. GINA; 2019; 1-21(V1.0) - inhaler technique (P.70)
5. Management of asthma in pregnancy; 2020; 1-9(v1.0) - signs of asthma (p.3).
6. Catherine Nelson-Piercy. Handbook of Obstetric Medicine 5th edition. 2015, 1-357
7. Kristi Isaac Rapp, Lovie Lewis Rodgers et al. Optimizing Patient Care in Asthma during Pregnancy. US Pharm. 2011;36;30-34
8. Rachel Enriquez, Pingsheng Wu et al. Cessation of asthma medication in early pregnancy. AJOG 2006; 195:149-53.
9. BTS-SIGN 158. British guideline on the management of asthma. 2003
10. NICE; 2020; MONTELUKAST - pregnancy (p.1)
11. Anna Dor-Wojnarowska, Marita Nittner-Marszalska et al. The long-term variability of FeNO in pregnant asthmatic women with controlled asthma. Department of Internal Medicine, Geriatrics and Allergology, Wroclaw Medical, University. Financing source: statutory activity project no ST542. 2013
12. Heather Powell, Vanessa E Murphy et al. Management of asthma in pregnancy guided by measurement of fraction of exhaled nitric oxide: a double-blind, randomised controlled trial. Lancet 2011;378;983–990
13. NICE Guidelines, NG80 2017; 1-39; Asthma: diagnosis, monitoring and chronic asthma management - Monitoring asthma control (p.23)
14. NICE Guideline, NG103, Flu vaccination: increasing uptake August; 2018; 1-73(v1.0)-vaccination for pregnant women (p.9)
15. Michelle H Goldie, Chris E Brightling. Asthma in pregnancy. The Obstetrician and Gynaecologist Journal 2013; 15:241-5
16. Greater Manchester and Eastern Cheshire SCN. Asthma in pregnancy guideline: 2019; 1-19
17. Azithromycin SPC. Accessible via (last accessed August 2020)

Dr Waseem Khan has received an honorarium from GSK for developing this article/content.

PM-GB-ASU-WCNT-200002 August 2020

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