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Asthma in pregnancy

Key learning points:

 - Current recommendations on the management of asthma in pregnancy

 - Effects and risks of asthma on the unborn fetus

 - Treating asthma safely during pregnancy and avoiding exacerbations


This article will provide an overview of asthma in pregnancy. The effects of asthma on pregnancy and recommendations for the use of treatment during pregnancy will be considered. Additionally, the effects of pregnancy on asthma, non-pharmacological management and management of the acute exacerbation will be discussed.

Asthma is a chronic inflammatory disorder of the airways which is characterised by cough, shortness of breath, chest tightness and intermittent episodes of wheeze.1

The disease can affect the trachea, the bronchi and the bronchioles which form part of the lower respiratory tract.2 Asthma causes inflammation and structural changes in the airways in response to certain stimuli and triggers. These can include hormonal triggers such as premenstrual conditions and pregnancy.1 

The prevalence of asthma in pregnant women is 4-12% which makes it the most common chronic condition in pregnancy.1 The 2012 British Thoracic Society and Scottish Intercollegiate Guideline Network (BTS/SIGN)3 provides guidance on the management of asthma that includes management of the condition in pregnancy and during labour. Several physiological changes occur during pregnancy that could worsen or improve asthma but the majority of women with the condition have normal pregnancies and the risk of complications is small in those whose asthma is well controlled.3

Effects of pregnancy on asthma

The natural history of asthma during pregnancy is extremely variable3 and it is therefore difficult to predict how asthma control will evolve for different women throughout the course of pregnancy.4 

It is suggested that a third of pregnant women will experience worsening asthma, a third will experience an improvement in overall symptoms, and for the remaining third, their asthma will remain unchanged.5 This commonly-quoted generalisation is confirmed by BTS/SIGN (2012) in the light of evidence from research studies.3 

Severe asthma is more likely to worsen during pregnancy than mild asthma.3 According to BTS/SIGN,3 studies suggest that 11-18% of pregnant women with asthma will have at least one emergency department visit for acute asthma, and of these, 62% will require hospitalisation. The occurrence of exacerbations is associated with the stage of pregnancy4 and is more common between 24 and 36 weeks.1 The risks associated with exacerbations include poor ante-natal care, respiratory viral infections, poor adherence to medication, lack of inhaled corticosteroids when indicated, and obesity.1,4 The relatively unpredictable course that asthma may take during pregnancy means that women with the disease should be closely monitored irrespective of disease severity.1,4

Effects of asthma on pregnancy

Asthma severity and poor asthma control are associated with adverse outcomes in pregnancy.4 Exacerbations during the first three months of pregnancy are associated with an increased risk of congenital malformation. 

Maternal asthma is associated with an increased risk of low birth weight, intrauterine growth retardation, pre-term delivery and pre-eclampsia. It is not clear whether poor maternal and fetal outcomes are directly attributable to asthma, secondary to the medications used in treating the disease, socioeconomic status or other factors.4 Despite an association between asthma and adverse outcomes in pregnancy, it remains clear that when asthma is well controlled there is little or no increased risk of adverse maternal or fetal complications.3

Using medication safely

According to BTS/SIGN3 pregnancy should be an indication to optimise therapy and maximise lung function in order to reduce the risk of acute exacerbation. However, pregnant women with moderate or severe asthma should be monitored closely to keep their asthma well controlled. It should be emphasised that it is safer for women to use asthma therapy in pregnancy to achieve good control than to have poorly controlled asthma.1 The risk of harm to the fetus from severe or chronically under-treated asthma outweighs any small risk from the medications used to control the disease.3 It is recommended that drug therapy in pregnancy should be given as for the non-pregnant patient.3 Inhaled short-acting bronchodilators (reliever inhalers) such as salbutamol or terbutaline are the first line of treatment for asthma. No significant association has been demonstrated between major congenital malformations or adverse perinatal outcomes and exposure to short-acting bronchodilators.3 

For patients with asthma who continue to experience symptoms, an inhaled corticosteroid (anti-inflammatory treatment) such as beclometasone dipropionate, budesonide or fluticasone propionate can be added to the treatment plan. Inhaled anti-inflammatory treatment has been shown to decrease the risk of an acute asthma attack in pregnancy and the risk of readmission following asthma exacerbation.3 If control of symptoms remains poor, a long-acting bronchodilator such as salmeterol or formoterol can be added to the treatment plan, and current evidence suggests that these treatments are safe in pregnancy.3 Finally, drugs such as theophylline, zafirlukast, montelukast and oral corticosteroids may be added for patients who experience persistently poor control of their asthma. BTS/SIGN advise that no significant association has been demonstrated between major congenital malformations or adverse perinatal outcomes following exposure to theophylline. Data regarding the safety of montelukast and zafirlukast in pregnancy is limited. However, the recommendation is that these drugs may be continued in women who were stable while on them prior to pregnancy.6

There is considerable evidence which demonstrates that steroid tablets are not teratogenic. However, there is some concern that oral steroids may be associated with oral clefts, pregnancy-induced hypertension, pre-eclampsia and pre-term labour. That said, it is important to note that studies of steroid exposure in pregnancy include patients with conditions other than asthma who were receiving steroids as a regular daily dose rather than as short courses which is how asthma patients would normally receive oral steroids. BTS/SIGN3 recommend that steroid tablets should be used as normal when indicated during pregnancy for severe asthma and should never be withheld because of pregnancy. 

Non-pharmacological management

Patient education is the key to successful asthma management.7 Education should include understanding of the condition, how to avoid triggers, appropriate use of inhaler devices and the importance of adherence to medication.1 Education about the safety of medication is especially important given that concerns are held by mothers and healthcare professionals that asthma drugs may have adverse effects on pregnant women and their babies.1 In pregnancy, women reduce their use of inhaled anti-inflammatory (corticosteroids) medication by 23%, short-acting bronchodilators by 13% for stable therapy and oral corticosteroids for exacerbations are reduced by 54%.1

The BTS/SIGN guideline makes the recommendation that education should be reinforced by a written action plan. Action plans provide advice about when and how to modify treatment, for example when to increase inhaled steroids or when to commence oral steroids. They also provide information about how to access help in response to worsening symptoms.7 Systematic reviews have shown that education and action plans lead to improvements in asthma control, reduce the need to seek emergency medical help and reduce hospital admissions.1

The acute attack in pregnancy

Pregnant women presenting with acute asthma exacerbations pose particular challenges, as an accurate assessment of the severity of the attack and prompt treatment can be life-saving.6 

Asthma exacerbations should be managed as per the BTS/SIGN (2012)3 guidelines which recommend that acute severe asthma in pregnancy should be treated vigorously in hospital. The guidelines also recommend that continuous fetal monitoring should be undertaken in situations where asthma is uncontrolled or severe. Assessment of respiratory function that includes physical examination is important to establish the severity of an exacerbation.6 In situations where the patient is unable to speak or provide a measurement of lung function, the exacerbation should be considered life-threatening.6 In acute exacerbations drug therapy should be administered as for a non-pregnant woman which includes nebulised bronchodilators and early administration of steroid tablets.3 Oxygen should be given to maintain saturation between 94-98% in order to prevent maternal and fetal hypoxia. In severe cases intravenous bronchodilators, aminophylline or intravenous bolus magnesium sulphate can be used as indicated.3 It is recommended that there is close liaison between respiratory physicians and obstetricians in the care of women who experience poorly controlled asthma in pregnancy, and women with acute severe asthma should be referred early to a critical care physician.3


Asthma is a chronic inflammatory disorder of the airways and is the most common chronic condition in pregnancy. The natural history of asthma during pregnancy can be extremely variable. Asthma severity and poor asthma control are associated with adverse outcomes in pregnancy but with appropriate pharmacological therapy, monitoring and education adverse maternal and fetal complications can be minimised. '



 1 Goldie MH, Brightling CE. Asthma in pregnancy. The Obstetrician & Gynaecologist 2013;15:241-5.

 2 Kaufman G. Asthma: pathophysiology, diagnosis and management. Nursing Standard 2011;26(5):48-56.

 3 British Thoracic Society/Scottish Intercollegiate Guidelines Network, British Guideline on the Management of Asthma, Revised Edition. 2012.

 4 Maselli DJ, Adams SG, Peters JI, Levine SM. Management of asthma during pregnancy. Therapeutic Advances in Respiratory Disease 2013;7(92):87-100.

 5 Benninger C, Mc Callister J. Asthma in pregnancy: Reading between the lines. The Nurse Practitioner 2010;35(4):10-8.

 6 Racusin DA, Fox KA, Ramin SM. Severe acute asthma. Seminars in Perinatology 2013;37:234-45.

 7 Kaufman G. Involving patients in asthma management and self-care. Independent Nurse 2012;19 November-2 December.