Hypertension in pregnancy (antihypertensive treatment)

NICE have stated that (1):

• in pregnancy labetalol is the first line treatment
  • only offer women with gestational hypertension antihypertensive treatment other than labetalol after considering side-effect profiles for the woman, fetus and newborn baby. Alternatives include methyldopa and nifedipine

General principles about use of antihypertensive medication in pregnancy:

• advise women who take antihypertensive treatments other than ACE inhibitors, ARBs, thiazide or thiazide-like diuretics that the limited evidence available has not shown an increased risk of congenital malformation with such treatment (1)
  
  
• labetolol (alpha and beta-blocker) is a commonly first line agent in hypertension in pregnancy - especially for resistant hypertension in the third trimester - other beta-blockers are less often used, especially before 28 weeks gestation, because of concerns that their use may lead to an inhibition of fetal growth
  
  
• methyl dopa is a centrally acting antihypertensive which is used as a second line agent for idiopathic hypertension or pre-eclampsia
  
  
• the calcium antagonist nifedipine is suggested as an alternative as a second-line drug for hypertension in pregnancy
  • the vasodilator drug hydralazine is sometimes used in pregnancy (seek expert advice)
    
    
• diuretics are not generally used in the management of hypertension in pregnancy - this is because diuretics have the theoretical potential to further reduce the circulatory volume in women with pre-eclampsia
  • NICE state that chlorothiazide diuretics (1):
    • may be an increased risk of congenital abnormality and neonatal complications if these drugs are taken during pregnancy
    • a woman should discuss other antihypertensive treatment with the healthcare professional responsible for managing their hypertension, if they are planning pregnancy
      
      
• ACE inhibitors are contra-indicated in pregnancy - they may cause oligohydramnios, hypotension, renal failure, and intra-uterine death in the fetus; ACE inhibitors (and Angiotensin Receptor Blockers) should be avoided by women who wish to become pregnant
  • NICE suggest that clinicians should advise women who take angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs):
    • that there is an increased risk of congenital abnormalities if these drugs are taken during pregnancy
    • alternative antihypertensive treatment should be discussed with the healthcare professional responsible for managing their hypertension, if a woman is planning pregnancy and taking an ACEI/ARB
    • alternative treatment should be discussed with the healthcare professional responsible for managing their condition, if ACE inhibitors or ARBs are being taken for other conditions such as renal disease
    • stop antihypertensive treatment in women taking ACE inhibitors or ARBs if they become pregnant (preferably within 2 working days of notification of pregnancy) and offer alternatives
      
      
• continue with existing antihypertensive treatment if safe in pregnancy, or switch to an alternative treatment, unless:
  • sustained systolic blood pressure is less than 110mmHg or
  • sustained diastolic blood pressure is less than 70mmHg or
  • the woman has symptomatic hypotension
    
    
• offer antihypertensive treatment to pregnant women who have chronic hypertension and who are not already on treatment if they have:
  • sustained systolic blood pressure of 140mmHg or higher or
  • sustained diastolic blood pressure of 90mmHg or higher
    
    
• when using medicines to treat hypertension in pregnancy, aim for a target blood pressure of 135/85mmHg
  
  
• consider labetalol to treat chronic hypertension in pregnant women
  • consider nifedipine for women in whom labetalol is not suitable, or methyldopa if both labetalol and nifedipine are not suitable
    • base the choice on any pre-existing treatment, side-effect profiles, risks (including fetal effects) and the woman's preference
      
      
• offer pregnant women with chronic hypertension aspirin75-150 mg once daily from 12 weeks
  
  
• offer placental growth factor (PlGF)-based testing to help rule out preeclampsia between 20 weeks and up to 35 weeks of pregnancy, if women with chronic hypertension are suspected of developing pre-eclampsia. (See the NICE diagnostics guidance on PlGF-based testing to help diagnose suspected preeclampsia)

The role of hypertension in maternal pathology remains uncertain. There is little evidence to indicate that seizures in pre-eclampsia are caused by hypertension or will be prevented by anti-hypertensive treatment. The control of hypertension serves as a useful expedient whilst awaiting definitive treatment - ie. delivery of the placenta.

Reference:

1. NICE (June 2019). Hypertension in pregnancy - the management of hypertensive disorders during pregnancy