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asthma in pregnancy

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Asthma is considered to be one of the commonest medical problems faced by a pregnant woman (1).

The effect of pregnancy on asthma is variable. Around a third of patients improve, a third worsen and a third continue unchanged (2)

  • a recent prospective cohort study of 1,739 pregnant women, an overall improvement in asthma in 23% and deterioration in 30.3% during pregnancy was seen
    • a systematic review concluded that, if symptoms do worsen, this is most likely to occur in the second and third trimesters, with the peak in the sixth month
  • there is also some evidence that the course of asthma is similar in successive pregnancies (3)

Increased progesterone and levels of free cortisol associated with pregnancy have bronchodilatory effects. This is countered by the reduced residual volume and increased PGF2 alpha secretion which promote bronchoconstrictor effects.

On the other hand uncontrolled asthma may cause several maternal complications (hyperemesis, hypertension, pre eclampsia) and fetal complications (fetal growth restrictions, pre term birth and neonatal hypoxia). There is no evidence of an increased risk of an asthmatic attack during labour.

Clinicians should offer pre-pregnancy counselling to women with asthma regarding the importance and safety of continuing their asthma medications during pregnancy since well controlled asthma throughout pregnancy has little or no increased risk of adverse maternal or fetal complications.

  • monitor pregnant women with moderate/severe asthma closely to keep their asthma well controlled.
  • advise women who smoke about the dangers for themselves and their babies and give appropriate support to stop smoking
  • women with asthma should be advised of the importance of good control of their asthma during pregnancy to avoid problems for both mother and baby (3)

Drug therapy in pregnancy (3):

  • beta 2 agonists
    • use short acting beta 2 agonists as normal
    • use long acting beta 2 agonists as normal
  • use inhaled steroids as normal
  • use oral and intravenous theophyllines as normal
  • use steroid tablets as normal when indicated for severe asthma. Steroid tablets should never be withheld because of pregnancy
  • leukotriene antagonists may be continued in women who have demonstrated significant improvement in asthma control with these agents prior to pregnancy not achievable with other medications (3)

Acute asthma in pregnancy (3):

  • give drug therapy for acute asthma as for the non-pregnant patient, including systemic steroids and magnesium sulphate
    • acute severe asthma in pregnancy is an emergency and should be treated vigorously in hospital
    • deliver oxygen immediately to maintain saturation 94-98%
    • continuous fetal monitoring is recommended for severe acute asthma
    • for women with poorly controlled asthma there should be close liaison between the respiratory physician and obstetrician, with early referral to critical care physicians for women with acute asthma (3)
  • management during labour
    • if anaesthesia is required, regional blockade is preferable to general anaesthesia
    • use prostaglandin F2 alpha with extreme caution because of the risk of inducing bronchoconstriction

Drug therapy in breastfeeding mothers (3):

  • encourage women with asthma to breast feed
  • use asthma medications as normal during lactation


  • advise women:
    • that acute asthma is rare in labour
    • to continue their usual asthma medications in labour
  • women receiving steroid tablets at a dose exceeding prednisolone 7.5 mg per day for > 2 weeks prior to delivery should receive parenteral hydrocortisone 100 mg 6-8 hourly during labour
  • in the absence of acute severe asthma, reserve caesarean section for the usual obstetric indications (4)


Last edited 11/2019 and last reviewed 01/2020