Pre-eclampsia Prophylaxis

Women who are at risk of pre-eclampsia should take Aspirin, 75mg OD from 12 weeks until the birth of the baby. 

Those who are at high risk of developing pre-eclampsia include:

  • hypertensive disease during previous pregnancies
  • chronic kidney disease
  • autoimmune disorders such as SLE or antiphospholipid syndrome
  • type 1 or type 2 diabetes

The classification of hypertension in pregnancy is usually defined as:

  • SBP > 140mmHg or DBP > 90mmHg
  • or an increase above booking reading of Systolic > 30mmHg  or diastolic > 15 mmHg

If you’ve decided they are hypertensive you need to categorise them into one of three groups:

  1. Pre-existing hypertension
  2. Pregnancy-induced hypertension (PIH aka Gestational hypertension)
  3. Pre-eclampsia

Pre-existing hypertension

  • History of hypertension before pregnancy or an elevated BP > 140/90 before 20weeks.
  • No proteinuria, No oedema
  • Occurs in 3-5% of pregnancies and is more common in older women

Pregnancy-Induced hypertension (PIH or Gestational Hypertension)

  • Hypertension (as defined above) occurring in the second half of pregnancy (after 20weeks)
  • No proteinuria, No Oedema
  • Occurs in around 5 – 7% of pregnancies
  • Resolves following birth (typically after a month).
  • Women with PIH are increase risk of future pre-eclampsia or hypertension in later life.


  • Pregnancy induced hypertension in association with:
  • Proteinuria (>0.3g/24hours)
  • Oedema may occur but is now less commonly used as a criteria
  • Occurs in around 5% of pregnancies.