see also:

• pregnancy

• SOB is a common symptom in pregnancy and is commonly physiologic in the 2nd half of pregnancy, but there are important conditions which need to be considered

• physiologic
• anxiety
• asthma
• pneumonia
• PE
• viral pneumonitis is more severe in pregnancy and often requires ICU - varicella in pregnancy, influenza
• anaemia
• acute pulmonary oedema (APO)
  • pre-eclampsia and eclampsia
  • sepsis / septicaemia - esp. pyelonephritis
  • cardiomyopathy - esp. peripartum
  • tocolytic Rx
  • rarely, phaeochromocytoma
• pleural effusion
  • ovarian hyperstimulation syndrome in those who have had IVF
  • severe pre-eclampsia and eclampsia
    • rarely, Mirror (Ballantyne) syndrome (severe PET, oedema, fetal and placental hydrops)
• rare causes:
  • amniotic fluid embolism - esp. peripartum
  • cardiac valvular disease
  • large pericardial effusions
  • pulmonary hypertension (PAH) - esp. peripartum and PH of either connective tissue (CT) disorders, congenital heart disease (CHD), pulmonary embolism (PE), antiphospholipid syndrome, obstructive sleep apnoea (OSA), HIV / AIDS or portal hypertension

• sinus tachycardia
• mild relative hypotension in 2nd trimester
• raised WCC, D-Dimer
• 5x risk of VTE compared to non-pregnant women
• progressive reduction of functional residual capacity (FRC) from 24wks gestation of up to 20-30% (400-700mL) due to reduced diaphragmatic excursion due to the uterine size
  • this is further reduced at term by 25% by supine posture
• NB. FEV1, PEFR remains unchanged although asthma tends to increase in pregnancy
• small pericardial effusions are common (15% in 1st TM - higher if IVF, 19% of those in 2nd TM, and nearly half of those in 3rd TM but resolve by end of puerperium)
• ECG changes:
  • variable degree of leftward shift of QRS axis
  • increased prominent Q waves in inf and ant-lat. leads
  • T wave flattening or inversion in III and V1-3
  • widened P wave
  • transient ST depression commonly occurs during LUSCS

• usual A,B,C's of resus as indicated
• careful Hx and exam (including BP, temp, SaO2) and targeted investigations
• in later half of pregnancy have patient sitting up to improve lung function
• consider some supplemental oxygen to keep SaO2 at least 92-94%
• if chicken pox lesions then isolate, negative pressure room and see varicella in pregnancy
• if wheezy, Rx as for asthma unless it is thought to be acute pulmonary oedema (APO)
• if an obvious cause is not evident, then:
  • FBE, U&E, LFTs, CRP, urinalysis
  • consider CXR (with pelvic shielding although this only reduced radiation dose to fetus by 3%¹⁾ however fetal radiation dose from a CXR is less than 0.0001mGy - a CTPA is 0.01-0.66mGy and a V/Q is 0.1-0.5 while the threshold for congenital abnormalities or growth restriction is thought to be 200mGy)
• if febrile:
  • consider rapid flu PCR swab and blood cultures
  • consider other causes of sepsis / septicaemia
• consider bedside Point of Care USS (POCUS):
  • can differentiate cardiogenic pulmonary oedema from non-cardiogenic causes of dyspnea with sens 94%, spec 92%
  • may be useful for detecting PE in those who are not suitable for either V/Q scan or CTPA (sens 87% spec 82%)
  • may be useful for evaluating pericardial effusion and cardiac function
  • may be useful for detecting DVT - absence of DVT makes PE unlikely and may avert need for V/Q scan
• if no cause evident and PE is possible then see Ix of suspected pulmonary embolism (PE)