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Asthma is the most common long-term medical condition encountered during pregnancy

It is estimated that 3–8% of pregnant women have asthma.1,2 Most women with asthma have normal pregnancies and the risk of complications is small if the asthma is well-controlled.3

Asthma during labour

Acute asthma exacerbations during labour are relatively rare with 80–90% of women having no asthma symptoms during labour and delivery, possibly due to the endogenous steroid production.3,4 If an exacerbation does occur, the patients normal asthma medication can be used and adjusted as required during this period.4

Pregnancy can affect the course of asthma

In general, during pregnancy the severity of asthma remains stable in one-third of women, worsens in one-third and improves in the remaining third. However, women with severe asthma are more likely to experience a worsening of symptoms than those with mild asthma.3,4 Deterioration is most likely in the second and third trimesters.3

The most common cause of exacerbations of asthma during pregnancy are viral respiratory infections and non-adherence to inhaled corticosteroids.4 A systematic review showed that pregnancy itself has no direct effect on FEV1.5

Poorly controlled asthma is associated with maternal and foetal complications

When asthma is well controlled during pregnancy, there is little or no increased risk of adverse maternal or foetal complications. Therefore, it is important to control asthma and minimise exacerbations by optimising treatment during pregnancy.

Compared to women without a history of asthma, women with asthma, particularly poorly controlled asthma, have been reported to have higher risks of several complications of pregnancy and delivery including, pre-eclampsia, haemorrhage, intrauterine growth restriction, pre-term delivery, low birth weight and increased perinatal mortality.1,3,6

Assess current asthma control in pregnant women

Clinical features used to assess current asthma control include (Table 1):1

  • Frequency and severity of symptoms (including how symptoms interfere with sleep or normal activity)
  • Frequency of use of short-acting beta-agonist for symptom control
  • History of exacerbations requiring the use of oral corticosteroids

Table 1: Assessment of asthma control in pregnant women (adapted from Schatz, 20091)
  Well-controlled asthma Asthma not well controlled Very poorly controlled asthma
Frequency of symptoms
≤ 2 days/week > 2 days/week Throughout the day
Frequency of nocturnal symptoms ≤ 2 times/month 1-3 times/week ≥ 4 times/week
Interference with normal activity None Some Extreme
Use of short-acting beta-agonist for symptom control
≤ 2 days/week > 2 days/week Several times/day
FEV1 or peak flow (expressed as the % of the predicted or personal best value) > 80% 60-80% < 60%
Exacerbations requiring use of oral corticosteroids
0–1 in past 12 months ≥ 2 in the past 12 months