FRCA Notes

Asthma during pregnancy

This page details only the elements of asthma management pertinent to pregnancy; see the asthma page from the ICM section for a more thorough overview.

Resources

  • 1% of parturients have asthma
  • 50% of women have a stable clinical course
  • 25% have improved symptoms
  • 25% show a deterioration in symptoms and it is usually those with more severe disease who follow this course

    • Factors aiding asthma Factors exacerbating asthma
    Progesterone-induced bronchial smooth muscle relaxation Reduced sensitivity to β-agonists
    Increased cortisol levels Increased prostaglandin levels causing bronchoconstriction
    Reduced cortisol sensitivity (as progesterone binds the receptor)
    Reluctance to take usual medications

  • Up to 10% of women will require hospital admission for an acute exacerbation during pregnancy
  • Asthmatic parturients are more likely to have complications such as pre-term delivery, low birth weight and pre-eclampsia

Ante-natal

  • Respiratory referral
  • Continuation of all regular treatment; no evidence of foetal harm from any asthma medications
  • Regular home assessment of peak flow to detect deteriorations early
  • Relative contraindication to use of β-blockers in management of pre-eclampsia

Intra-partum

  • Continue all regular medications, despite the possible uterine effects of β-agonists
  • May require steroid cover
  • Epidural analgesia is beneficial to avoid pain-associated hyperventilation, which can precipitate acute attacks in some patients
  • Prostaglandin analogues are contraindicated in the management of uterine atony
  • Regional anaesthesia is preferable to GA, as with virtually every parturient

Acute attacks

  • Acute attacks may cause maternal hypoxia and hypocapnoea
  • This reduces foetal oxygen delivery via vasoconstriction of the umbilical artery and left-shift of the oxyHb-dissociation curve
  • Management is the same as for non-pregnanct patients
    • One difference is a patient should be deemed to be 'tiring' at a PaCO2 of 4.0kPa, rather than a normal PaCO2, owing to the lower levels during pregnancy