Key content
 Asthma is a common condition that affects ~10% of pregnant
women.
 Pregnancy worsens asthma control in one-third of women,
improves it in one-third and has no effect on one-third.
 Poor asthma control has adverse effects upon maternal and fetal
outcomes.
 Good asthma management to maintain control is important in line
with national guidelines.
 Standard therapy with inhaled corticosteroids with or without the
addition of short and long-acting b-agonists can be used in
pregnancy.
Learning objectives
 Comprehensive overview of asthma in pregnancy.
 Review asthma management in pregnancy.
Ethical issues
 Are women appropriately counselled on the pregnancy risks of
asthma?
 Are doctors aware of the safety of routine asthma treatments in
pregnancy?
Keywords: asthma / b-agonists / corticosteroids / pre-eclampsia /
pregnancy

Introduction
Asthma affects an estimated 235 million people worldwide
and the burden is likely to rise substantially in the
next few decades.1–3 The condition causes about 239 000
deaths per year (0.4% of all deaths due to disease) and
results in a large burden of disability. The total cost of
asthma in Europe is estimated to be €17.7 billion
per annum.2
Asthma is a chronic inflammatory disease of the airways,
which is characterised by intermittent episodes of wheeze,
shortness of breath, chest tightness and cough, which are
often worse at night. It is a variable disease where
inflammation and structural changes can occur in the
airway in response to certain stimuli or triggers (Box 1).3,4
This causes airway hyper-responsiveness and variable
airflow obstruction leading to the symptoms described.
Patients suffer from flare-ups or exacerbations of their
disease either in response to an acute infection, which is
usually viral in origin, or due to poor control of their
airway inflammation.
The prevalence of asthma in pregnant women is 4–12%,
making it the most common chronic condition in
pregnancy.5,6 Pregnancy can affect asthma control and conversely asthma can affect pregnancy. Importantly, the
British Thoracic Society/Scottish Intercollegiate Guideline
Network (BTS/SIGN) asthma guideline on the management
of asthma apply in pregnancy and good asthma control
during pregnancy is critical.

Triggers for asthma
 Allergens, such as house dust mite, pollen, etc.
 Smoking
 Exercise
 Occupational exposure
 Pollution
 Drugs, such as aspirin, b-blockers
 Food and drinks such as dairy produce, alcohol, peanuts and orangejuice
  Additives such as monosodium glutamate and tartrazine
 Medical conditions, such as rhinitis and gastric reflux
 Hormonal, such as premenstrual conditions and pregnancy

Breathlessness in pregnancy
Breathlessness is the sensation of feeling out-of-breath or
unable to catch your breath. A healthy respiratory rate is 12–20 breaths/minute at rest. A persistent respiratory rate
at rest >24 breaths/minute is abnormal. Breathlessness in
pregnancy is extremely common and may reflect either
the normal anatomical and physiological changes that
occur in pregnancy, or anxiety, or may be a consequence
of an underlying pathology. Therefore, in a woman with
known asthma the cause of increased breathlessness may
not be due to asthma. Similarly, in a woman not
diagnosed as asthmatic new incident asthma can be the
cause of breathlessness, albeit rarely.

Main differential diagnoses in pregnant women with dyspnoea
 Anxiety
 Hyperventilation
 Dysfunctional breathing
 Respiratory disease:
– asthma
– chest infection and/or pneumonia
– thromboembolic disease
– interstitial lung disease, e.g. sarcoid or secondary to a connective
tissue disorder
– pneumothorax
– amniotic fluid embolism
 Cardiac disease:
– arrhythmias
– ischaemic heart disease
– cardiomyopathy
 Endocrine disease:
– diabetes mellitus leading to hyperventilation in the setting of
acute ketoacidosis
– acute thyrotoxicosis
 Haematological:
– chronic anaemia
– acute haemorrhage
 Renal disease:
– hyperventilation to compensate for metabolic acidosis secondary to acute renal failure

Physiological factors affecting asthma in pregnancy
 Increase in free cortisol levels may protect against inflammatory
triggers.
 Increase in bronchodilating substances (such as progesterone) may
improve airway responsiveness.
 Increase in bronchoconstricting substances (such as prostaglandin
F2a) may promote airway constriction.
 Placental 11b-hydroxysteroid dehydrogenase type 2 decreased
activity is associated with an increase in placental cortisol
concentration and low birthweight.
 Placental gene expression of inflammatory cytokines may promote
low birthweight.
 Modification of cell-mediated immunity may influence maternal
response to infection and inflammation.

Pregnancy issues
 Poorly controlled asthma confers an increased risk to the mother
and fetus.
 Asthmatic women are more at risk of low birthweight neonates,
preterm delivery and complications such as pre-eclampsia, especially
in the absence of actively managed asthma treated with inhaled
corticosteroids, although the increased risk is very small in women
with well-controlled asthma.
 There is no contraindication to most first-line treatments for asthma
when used in pregnancy.
 Smoking cessation is an important part of general obstetric advice,
but is important in asthma to reduce symptoms and the efficacy of
inhaled corticosteroids is reduced in asthmatics who smoke.
 Exacerbations of asthma should be managed in line with current
guidelines from British Thoracic Society/Scottish Intercollegiate
Guidelines Network.

Management of stable asthma in
pregnancy
The management and treatment of asthma are generally the
same in pregnant women as in non-pregnant women and in
men.7 The intensity of antenatal maternal and fetal
surveillance should be based on the severity of asthma, i.e.
current need for therapy, symptom control, exacerbation
frequency including high-dose corticosteroid usage and
hospitalisation and lung function, for example, peak flow
and spirometry together with the risk of fetal complications.
The general principles of asthma management in pregnancy
are summarised in Box 4. Women with moderate to severe asthma treatment step 3 or above need to be
managed by both a respiratory physician and obstetrician to
optimise asthma control.

Management of asthma exacerbations in
pregnancy
Asthma exacerbations are managed as per the BTS/SIGN
guidelines,7 which include the use of oral corticosteroids,
nebulised b2-agonists and oxygen as well as other additional
supportive care dependent upon severity.
Asthma: labour and delivery
Asthma does not usually affect labour or delivery with less
than a fifth of women experiencing an exacerbation during
labour,8 and severe or life-threatening exacerbations are very
rare. Prostaglandin F2a (for example, Hemabate®, Pfizer Ltd.,
Sandwich, UK) can cause bronchospasm and needs to be
used with caution, whereas prostaglandin E2 (for example,
Prostin®, Pharmacia Ltd., Sandwich, UK) is not associated
with bronchospasm. Box 5 outlines the key points for
women with asthma during labour.

Peripartum issues
 Acute, severe or life-threatening exacerbations of asthma during
labour are extremely rare.
 Women who have been on regular oral steroids may require
hydrocortisone during labour.
 Ergometrine, Syntometrine and prostaglandin may cause
bronchoconstriction and should be used with caution.
Asthma: postpartum and breastfeeding
In the postpartum period there is not an increased risk of
asthma exacerbations and within a few months after delivery a
woman’s asthma severity typically reverts to its pre-pregnancy
level.5 Few data are available on the safety of asthma drugs in
breastfed neonates, but in general the same medications
deemed safe in pregnancy can be continued and those with a
negative or an uncertain safety profile should be avoided.
Non-steroidal anti-inflammatory drugs (NSAIDs) for
analgesia are to some degree contraindicated in asthma and
may cause bronchospasm but in women without intolerance
to NSAIDs they can be used.
Primary care physicians can manage most women with
asthma, but women with severe disease, particularly if
systemic corticosteroids are considered, need to be
managed by respiratory physicians.
The World Health Organization recommends that women
should exclusively breastfeed for at least 6 months.25 Whether
breastfed children have a reduced risk of developing allergic
disease including asthma is unproven, but this does not
detract from the overwhelming benefit of breastfeeding.
Conclusion
Asthma is a widespread condition that affects ~10% of
pregnant women. Poor asthma control has adverse effects
upon maternal and fetal outcomes. Good asthma
management to maintain control is therefore important
and standard therapy with inhaled corticosteroids with or
without the addition of short- and long-acting b-agonists
may be used in pregnancy.