Asthma, often complicated by allergies, is a common health problem that can cause complications in pregnancy (World Health Organization (WHO), 2014). The UK has an asthma prevalence during pregnancy of around 8% (Clark et al, 2007), although more recent epidemiological data is unavailable. With the prevalence and morbidity associated with asthma increasing, midwives are likely to care for women with varying degrees of asthma control. It is therefore imperative that there be prompt recognition and intervention to promote optimal perinatal outcomes. Asthma, often accompanied by allergic rhinitis (Angier et al, 2010), can be well-controlled and devastating consequences avoided with careful attention.
Asthma definition and pathophysiology
Asthma is a ‘chronic inflammatory disorder of the airways in which many cells and cellular elements play a role: in particular, mast cells, eosinophils, T-lymphocytes, macrophages, neutrophils, and epithelial cells’ (Murdock, 2002: 28). It is characterised by exposure to a precipitating factor (or trigger), which narrows the airways and obstructs airflow (National Asthma Education and Prevention Program (NAEPP), 2007). The obstruction is usually reversible, either spontaneously or with treatment. Asthma triggers, including allergens or irritants, can lead to several responses in the initial acute stage where there is a susceptible individual who is exposed for a long enough period of time. These responses are classified as early (immediate), late phase, dual phase, and recurrent asthmatic reaction.
The early reaction is a result of mast cell activation and gives rise to bronchial smooth muscle contraction (bronchospasm) within minutes of exposure to a trigger. This process is often the result of immunoglobulin E (IgE)-dependent release of mediators from mast cells and is accompanied by mucosal oedema and mucus plug formation causing decreased air flow rates, particularly when exhaling. As air becomes trapped within the alveoli, lungs become hyper inflated with a subsequent ventilation perfusion mismatch. Blood gas analysis may initially show hypoxemia with carbon dioxide tensions that are generally normal or reduced due to compensatory hyperventilation. However, with the failure of these compensatory mechanisms as an individual fatigues, retention of carbon dioxide occurs giving rise to a respiratory acidosis (Murdock, 2002; British Thoracic Society/Scottish Intercollegiate Guidelines Network (BTS/SIGN), 2013). The response usually peaks within 15–20 minutes and subsides within 1 hour. A late phase reaction may occur due to activation of eosinophils and other inflammatory cells, occurring 12–24 hours after exposure. Dual phase reaction is the occurrence of the early reaction and the late phase reaction in the same individual. Sometimes, a susceptible individual may exhibit airway hyper-responsiveness for the subsequent days after the exposure. This is known as the recurrent asthmatic reaction (Murdock, 2002), often accompanied by wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. Persistent varying change in airway structure occurs over time in most asthma patients (NAEPP, 2007).
Changes in asthma and allergies during pregnancy
There are multiple pulmonary changes that are normal during pregnancy (Figure 1). The respiratory rate remains relatively unchanged during pregnancy but there is a reduction in functional residual capacity as the uterus enlarges, displacing the diaphragm 4–5 cm upwards (Vatti and Teuber, 2012). Dyspnoea is normal during pregnancy with the minute volume increasing by 40–50% to compensate for the increased oxygen demand of pregnancy. This change begins in the first trimester, peaks in the second trimester, and becomes relatively stable in the third trimester. The physiologic hyperventilation is due to an increased tidal volume which is the result of the stimulatory effect of progesterone on the respiratory centre. When dyspnoea is accompanied by wheezing and/or coughing, however, it is likely to be caused by asthma (Vatti and Teuber, 2012).
Most pregnant women with asthma, as well as those with allergies, experience changes in the condition during pregnancy, which are thought to be due to fluctuating hormone levels and tend to follow what has been termed the ‘rule of thirds’. That is, one third of women will maintain similar asthma or allergy control during pregnancy, one third of women will improve, and another third will worsen (Murphy and Gibson, 2011; BTS/SIGN, 2013). These changes are unpredictable, although poorly controlled asthma in the pre-pregnancy period is a predisposing factor for it worsening during pregnancy (Murphy and Gibson, 2011; Tamasi et al, 2011; Vatti and Teuber, 2012). There is also a tendency for asthma control to be similar in successive pregnancies (Rance and O'Laughlen, 2013).
Asthma exacerbation may occur at any time during pregnancy though is most likely between 29 and 36 weeks gestation (BTS/SIGN, 2013); exacerbation of allergies is most likely in the third trimester (American College of Allergy, Asthma and Immunology, 2010). Rhinitis, sinusitis, and gastro-oesophageal reflux (GERD) often co-exist with asthma and can be especially troublesome during pregnancy, and exacerbate asthma (NAEPP, 2007).
The main trigger for asthma is believed to be respiratory viruses (Jackson et al, 2011) with pregnant women particularly susceptible due to changes in cell-mediated immunity during pregnancy. Respiratory tract infection, a history of severe asthma, inadequate antenatal care, and a lack of appropriate treatment with inhaled corticosteroids also contribute to asthma exacerbation (Murphy and Gibson, 2011; Rance and O'Laughlen, 2013), as can obesity (Tamasi et al, 2011) and non-adherence to prescribed medication. The latter is of particular significance as almost one third of pregnant women report non-adherence to prescribed medication before a severe exacerbation (Murphy and Gibson, 2011).
Perinatal outcome
With asthma exacerbation there is increased risk of adverse perinatal outcome (Blais and Forget, 2008). Maternal asthma can cause hypoxia combined with respiratory alkalosis that decreases placental blood flow. When maternal oxygen falls rapidly during an exacerbation, fetal oxygen saturation can be compromised. It should be noted that fetal distress may occur despite a lack of evidence of maternal hypotension or hypoxia so it is important to continuously monitor the fetal heart during an acute asthma exacerbation (Rance and O'Laughlen, 2013). The fetus can normally compensate for acute hypoxemia in a number of ways, but poor control over a prolonged period of time may exceed compensatory mechanisms. Lack of oxygen to the baby and the long-term effect of hypoxemia could affect fetal growth (Firoozi et al 2010; Rocklin 2011). With poorly controlled, worsening, or severe asthma, the baby is at risk for low birth weight (Murphy et al, 2005). Poorly controlled asthma has also been associated with preterm birth (Bakhireva et al, 2008), pre-eclampsia (Vatti and Teuber, 2012), and gestational diabetes (Bain et al, 2014).
Severity of asthma symptoms during pregnancy may also be influenced by the baby's gender. Carrying a female baby is associated with asthma exacerbations and a near double incidence of hospitalisation for asthma (Bakhireva et al, 2008) as well as a higher incidence of intrauterine growth restriction (IUGR) (Rocklin, 2011; Tamasi et al, 2011). The biological mechanisms which explain the differential effects of the baby's gender on maternal asthma are unknown.
Maternal asthma is a risk factor for caesarean birth. Some studies have found an increase in complications such as placental abruption and premature rupture of membranes, which might contribute to the higher rate of caesarean births among women with asthma (Murphy and Gibson, 2011). The risk for operative birth in pregnant women with severe asthma is most likely due to provider concerns for the safety of normal birth (Blais et al, 2014). Unless there is acute severe asthma, caesarean birth is not indicated (BTS/SIGN, 2013).
Diagnosis
Pregnant women with asthma usually have a known history with diagnosis based on history, physical examination and pulmonary function tests. Typical symptoms of asthma are wheezing, cough, chest tightness and dyspnoea. Asthma symptoms generally become worse at night and in the presence of specific environmental stimuli. When poorly controlled or with symptomatic asthma, expiratory wheezing may be present. The demonstration of a reduced forced expiratory volume in 1 second (FEV1) or FEV1/FVC (forced vital capacity) with an FEV1 improvement of greater than or equal to 12% and 200 ml following bronchodilator administration confirms the diagnosis of asthma (Tamasi et al, 2011; Vatti and Teuber, 2012). Other methods for confirming an asthma diagnosis include specific challenges, the most common of which is the methacholine challenge, which is contraindicated during pregnancy and lactation and should be done before or after if the diagnosis is equivocal. Testing should be done in a pulmonary lab in consultation with a chest physician. Spirometry testing is recommended for asthma diagnosis in pregnancy (NAEPP, 2007; BTS/SIGN, 2013). When pregnant women present with dyspnoea, spirometry helps to distinguish between an asthma flare-up and normal physiological changes during pregnancy as women with asthma will have reduced volumes that can be exhaled.
In addition to an accurate diagnosis of asthma (Table 1), determination of allergy is also important during pregnancy as many asthmatics are atopic, and avoidance of allergen triggers is important. Those with allergic rhinitis may complain of anterior rhinorrhea, sneezing, nasal obstruction and pruritus, and often have conjunctivitis (Brozek et al, 2010), significantly complicating asthma where present. Immunotherapy for allergy is not normally recommended during pregnancy as potent antigens can cause anaphylaxis, particularly early in the course of therapy when doses are often increased rapidly (Namazy and Schatz, 2014). When determination of allergy is necessary, blood tests for specific IgE measurement can be utilised (Tamasi et al, 2011; Vatti and Teuber, 2012). For women receiving allergy shots prior to pregnancy, treatments can be continued, although allergists will generally avoid increasing the dose during pregnancy for those women who have not yet reached their maintenance. Following birth, a woman can resume escalation of her allergy injections.
| Location of airway problem | Disease/condition |
|---|---|
| Upper airway disease | Allergic rhinitis |
| Sinusitis | |
| Airway obstruction | Foreign body |
| Vocal cord dysfunction | |
| Cystic fibrosis | |
| Viral bronchiolitis | |
| Bronchopulmonary dysplasia | |
| Congenital heart disease | |
| Chronic obstructive pulmonary disease | |
| Lung cancer | |
| Sarcoidosis | |
| Other | |
| Gastroesophageal reflux | |
| Psychogenic cough | |
| Pulmonary embolism | |
| Heart failure |
Clinical management
Determining control
Each antenatal visit should assess for pulmonary functioning and asthma control as control of symptoms is crucial in clinical management (Table 2). A helpful tool in the clinical evaluation of asthma control is the Asthma Control TestTM (ACTTM) (Quality Matters, 2014). Both reliable and valid for use, this five-question test related to asthma control is available for women to complete online or can be printed and administered during clinic visits. A composite score of 16 or less during pregnancy suggests that the asthma may not be well-controlled and that further evaluation should be undertaken (Monteiro de Aguiar et al, 2014; Quality Matters, 2014).
| Parameter | Well-controlled | Not well-controlled | Very poor control |
|---|---|---|---|
| Frequency of symptoms | <2 days/week | >2 days/week | Throughout the day |
| Frequency of nighttime awakening | <2 times/month | 1–3 times/week | >4 times/week |
| Interference with normal activity | None | Some | Extreme |
| Use of short-acting ß-agonist for symptom control | <2 days/week | >2 days/week | Several times/day |
| FEV1 or peak flow (% of the predicted or personal best value) | >90 | 60–80 | <60 |
| Exacerbations requiring use of systemic corticosteroid (number) | 0–1 past 12 months | >2 in past 12 months |
* Data are from the National Asthma Education and Prevention Program (2007)
The level of control is based on the most severe category
The frequency and effect of symptoms should be assessed according to the patient's recall of the previous 2 to 4 weeks
FEV1 denotes forced expiratory volume in 1 second
In addition to subjective asthma control, pulmonary function should be assessed at each visit. Spirometry is preferred, although it is acceptable to assess control from peak flow readings which measure air outflow from the lungs. Where asthma is not well-controlled, step-up therapy should be implemented. Step therapy involves a stepwise approach in use of asthma medications to manage asthma, including during pregnancy. Steps progress from 1 to 5 with a higher step indicative of more aggressive pharmacologic treatment (BTS/SIGN, 2013) (Table 3).
| Step | Symptom control | Preferred controller medication |
|---|---|---|
| 1 | Mild intermittent asthma | Inhaled short-acting beta2 agonist as required |
| 2 | Regular preventive therapy | Add inhaled corticosteroid 200–800 µg/day* (400 µg/day is an appropriate starting dose) |
| Start at dose of inhaled corticosteroid appropriate to disease severity | ||
| 3 | Initial add-on therapy | Add inhaled long-acting beta2 agonist (LABA) |
| Assess and continue with good control | ||
| If control not good, increase inhaled corticosteroid to 800 µg/day* (if not already at that dose) | ||
| If no response to LABA, stop; increase inhaled corticosteroid to 800 µg/day* | ||
| If corticosteroid is already at 800 µg/day and control not improving, stop | ||
| Start leukotriene receptor antagonist or theophylline SR | ||
| 4 | Persistent poor control | Consider trials of: |
| Increasing inhaled corticosteroids (up to 2000 µcg/day*) | ||
| Addition of a fourth drug (e.g. leukotriene receptor antagonist, theophylline SR, beta2 agonist tablet | ||
| 5 | Continuous or frequent use of oral steroids | Use daily steroid tablet in lowest dose providing adequate control |
| Medium high dose inhaled corticosteroid at 2000 µg/day* | ||
| Consider other treatments to minimise the use of steroid tablets | ||
| Refer patient for specialist care |
Pharmacologic treatment
Although perinatal safety of commonly used asthma medications, particularly long-acting beta2agonists, has not been conclusively determined, midwives should prescribe and encourage use for control because the benefit of doing so outweighs the potential risk (Gregersen and Ulrik, 2013; Maselli et al, 2013). Pharmacologic management of asthma during pregnancy is the mainstay of control and commonly involves the use of inhaled corticosteroids, sometimes with the addition of a long-acting beta2 agonist in women with moderate-to-severe persistent asthma. For any asthmatic experiencing acute symptoms, short-acting beta2agonists remain the medication of choice. The preferred short-acting beta2agonist is salbutomol, which has a good safety profile (Murphy and Gibson, 2011) with benefits likely outweighing risks in pregnancy.
Corticosteroids are companion drugs often used with beta2 agonists. Inhaled corticosteroids (ICS) are preferred and have proven efficacy; oral corticosteroids, although not teratogenic, have been linked to IUGR. ICS are effective as a preventive therapy because of their broad action on inflammatory processes (BTS/SIGN, 2013). Where alternate medications are needed, theophylline, sodium cromoglygate, or a leukotriene receptor antagonist can be considered. A medication used for severe persistent allergic asthma is omalizumab, a monoclonal antibody targeting the immunoglobulin E (IgE) molecule, which should be continued during pregnancy for those women on this therapy prior to conception.
Long-acting beta agonist (LABA), combination ICS/LABA and leukotriene antagonist should be used with caution during pregnancy and lactation as they have not been well studied. In general, LABAs should be used for the shortest period of time possible and in combination with an ICS (BTS/SIGN, 2013).
Despite evidence-based guidelines for treatment, pregnant women who have asthma are often undertreated. When compared to non-pregnant controls, pregnant women with asthma who presented to the emergency department were less likely to receive indicated corticosteroids (McCallister, et al, 2011). When asthma is not controlled, step-up therapy should be implemented. However, the midwife should first review medication technique, adherence to the treatment, and environmental control (BTS/SIGN, 2013). A step-down therapy may be considered where there is good control but it may be prudent to do so following birth to avoid the potential for asthma to worsen as a result.
Treating allergic rhinitis
If avoidance of aeroallergens is not possible or is insufficient in preventing symptoms, pharmacotherapeutics should be added (Incaudo and Takach, 2006). Intranasal corticosteroids (e.g. budesonide) are effective and safe in treating allergic rhinitis during pregnancy and lactation (Angier et al, 2010). A leukotriene receptor antagonist, montelukast, could be considered as well (Murphy and Gibson, 2011).
Antihistamines, both oral and intranasal, are also effective in the treatment of allergic rhinitis. An advantage of the intranasal formulation is that it has an effect on nasal congestion, which is not seen with oral antihistamines. Of the oral antihistamines, the first generation (e.g. diphenhydramine, chlorpheniramine) are more potent but can cause side effects, such as sedation and anticholinergic symptoms. Although none of the first generation antihistamines have been studied in pregnant women, they have been on the market much longer and their safety is generally reassuring (Gilboa et al, 2014). Second generation antihistamines (e.g. loratadine, cetirizine) are longer acting, have fewer side effects, and are available without prescription (Namazy and Schatz, 2014). A systematic review of the literature related to use of antihistamines and birth defects was reassuring for safety although does note reports of a link between use of loratadine and hypospadias (Gilboa et al, 2014). While subsequent research has not confirmed the link, risk and benefit of medications should always be considered.
Where nasal congestion is a problem, intranasal steroid sprays or intranasal antihistamines can be used. Other nasal sprays are also available, including cromolyn and ipratropium; the latter is an effective option as add-on therapy or even monotherapy for women whose main complaint is rhinorrhea. Delivery of medication will be maximised where nasal saline irrigation or nasal saline sprays are first used before administration of medicated sprays. In dry climates where nosebleeds or nasal irritation from dryness are more common, nasal saline gel can be very helpful.
Oral decongestants should be avoided due to their systemic side effects and the fact that they cause vasoconstriction, which is contraindicated during pregnancy. Although topical decongestant sprays do not have the same systemic absorption, they should also be avoided as they too act via vasoconstriction and their use may therefore result in rhinitis medicamentosa, a condition defined by rebound nasal congestion. Similarly, use of varied complementary and alternative medicine approaches (e.g. acupuncture, homeopathic remedies, herbal medicines) is not recommended due to a lack of evidence (ARIA, 2010).
Pregnancy care with asthma
The first antenatal visit should include a determination of asthma control in prior pregnancies, where applicable, with plans made for follow-up based on the extent of asthma control. Some women may be able to follow the standard schedule for antenatal visits while others may need to be seen more frequently. Schatz and Dombrowski (2009) recommend that pregnant women have follow-up every 1–2 weeks until there is good asthma control, then at least monthly until birth.
Midwives should consider the need for collaboration with a chest physician, allergy nurse, general practitioner, practice nurse and/or maternal-fetal medicine specialist, where pharmacotherapy involves more than just an inhaled corticosteroid for maintenance and a short-acting beta2agonist for rescue, or where symptoms are severe and control cannot be achieved.
Fetal monitoring
The baby's wellbeing should be regularly monitored throughout the antenatal and intrapartum period, particularly where the baby is known to be female. Where growth concerns manifest, serial ultrasounds should be considered at 2–3 week intervals (American College of Obstetrics and Gynaecology, 2008). When control of asthma cannot be documented, there should be extra vigilance using other surveillance strategies to include non-stress testing, amniotic fluid index, and biophysical profile. Daily fetal movement counts should be encouraged as well.
Intrapartum considerations
Labour care
Substantial asthma symptoms are not uncommon during the intrapartum period, although exacerbation is relatively rare during labour and birth. However, women should be reminded to bring their medications to the birthing centre or hospital when in labour or to have them available in the case of a planned home birth. Asthma symptoms are typically easily controlled with the women's established medication regimen. Other medications commonly used during the intrapartum period can be used without concern. Medications to induce or augment labour, such as oxytocin or syntocinon, misoprostol (prostaglandin E1 analogue), and the E2 prostaglandins, are considered safe for use in women with asthma (BTS/SIGN, 2014). Carboprost, however, should not be used for postpartum haemorrhage in women with asthma as it is a potent broncho constrictor (Briggs et al, 2011).
Postpartum considerations
Women with asthma should be encouraged to exclusively breastfeed for a minimum of 3-6 months as doing so may have a protective effect for development of asthma and allergies (Friedman and Zeiger, 2005; Brozek et al, 2010; BTS/SIGN, 2014). Most pregnant women with asthma will revert to their pre-pregnant asthma status within 3 months of giving birth (Hanania et al, 2011).
Patient education
Every pregnant woman should have an asthma action plan that details individualised, specific instructions including daily medications, warning signs and symptoms, what to do if symptoms worsen, and emergency home care. Women should also be counselled and reminded to actively participate in strategies to control asthma and allergy symptoms. The midwife should stress that many of the triggers that cause asthma to worsen or contribute to exacerbations can be controlled by the woman (Table 4).
| Treatment | Frequency |
|---|---|
| Asthma control | Determine severity at baseline (spirometry recommended) |
| Assess at each prenatal visit | |
| Pulmonary function | Assess at each visit using spirometer or peak flow meter |
| Provide patient with a peak flow meter and instruct in use | |
| Implement step therapy |
|
| Education | Discuss factors which may exacerbate symptoms |
| Avoid stopping or changing medications without first discussing with the midwife and/or physician | |
| Plan to bring medications to hospital or birth centre when in labour, or have available if a planned home birth | |
| Model of care | Implement an interdisciplinary model to monitor and educate patients |
In addition to lifestyle measures that can minimise asthma symptoms, including avoidance of known triggers and treatment of comorbidities, midwives should discuss with women the importance of taking prescribed medications as ordered; medications should not be stopped or dosages changed without talking with the midwife or other obstetrical provider.
Finally, consideration should be given to development of an interdisciplinary model of care to monitor pregnant women with asthma and to provide effective educational strategies. Research has demonstrated better maternal outcomes where interdisciplinary efforts addressed asthma control (Lim et al, 2014). An interdisciplinary effort may also help to mitigate unnecessary interventions such as caesarean birth.
Conclusions
Midwives can play a crucial role in the control of asthma and allergies and in preventing exacerbations, which are particularly worrisome during pregnancy where gestational changes compound demands on maternal systems. Fetal wellbeing may be compromised where monitoring, education, and intervention fail to be initiated. Careful assessment and prompt intervention can improve asthma control to help ensure positive outcome for both mother and baby. When asthma and allergies are optimally controlled, perinatal outcomes are as good as for those women without the disease (Osur, 2005; Kennedy, 2009). Midwives should work in collaboration with the GP or practice nurse specialising in asthma management to provide the best care for women with asthma.