maternal hypertension in pregnancy

Last edited 01/2022 and last reviewed 04/2023

Hypertensive disorders during pregnancy affect around 8% to 10% of all pregnant women and can be associated with substantial complications for the woman and the baby

• women can have hypertension before pregnancy or it can be diagnosed in the first 20 weeks (known as chronic hypertension), new onset of hypertension occurring in the second half of pregnancy (gestational hypertension) or new hypertension with features of multi-organ involvement (pre-eclampsia)

During pregnancy hypertension is defined as:

• blood pressure of 140mmHg systolic or higher, or 90mmHg diastolic or higher

Severe hypertension

• blood pressure over 160 mmHg systolic or over 110 mmHg diastolic.

Gestational hypertension

• new hypertension presenting after 20 weeks of pregnancy without significant proteinuria

When using medicines to treat hypertension in pregnancy, aim for a target blood pressure of 135/85mmHg

NICE have defined pre-eclampsia as (1):

• new onset of hypertension (over 140 mmHg systolic or over 90 mmHg diastolic) after 20 weeks of pregnancy and the coexistence of 1 or more of the following new-onset conditions:
  
  
  • proteinuria (urine protein:creatinine ratio of 30mg/mmol or more or albumin:creatinine ratio of 8mg/mmol or more, or at least 1 g/litre [2+] on dipstick testing) or
    
    
  • other maternal organ dysfunction:
    • renal insufficiency (creatinine 90 micromol/litre or more, 1.02 mg/100 ml or more)
    • liver involvement (elevated transaminases [alanine aminotransferase or aspartate aminotransferase over 40 IU/litre] with or without right upper quadrant or epigastric abdominal pain)
    • neurological complications such as eclampsia, altered mental status, blindness, stroke, clonus, severe headaches or persistent visual scotomata
    • haematological complications such as thrombocytopenia (platelet count below 150,000/microlitre), disseminated intravascular coagulation or haemolysis
      
      
  • uteroplacental dysfunction such as fetal growth restriction, abnormal umbilical artery doppler waveform analysis, or stillbirth

Severe pre-eclampsia

• pre-eclampsia with severe hypertension that does not respond to treatment or is associated with ongoing or recurring severe headaches, visual scotomata, nausea or vomiting, epigastric pain, oliguria and severe hypertension, as well as progressive deterioration in laboratory blood tests such as rising creatinine or liver transaminases or falling platelet count, or failure of fetal growth or abnormal doppler findings

Antihypertensive treatment of hypertension in pregnancy

• labetalol and nifedipine are recommended by national guidelines and commonly used in clinical practice to reduce the risk of developing severe hypertension in these women (2)
  • there is little evidence from head-to-head comparisons of effectiveness and tolerability to guide choice of antihypertensive treatment in pregnancy, and uncertainty about impact on clinical outcomes such as stroke, pre-eclampsia, perinatal death, fetal growth restriction, or preterm birth
  • antihypertensive treatment for mild to moderate hypertension in pregnancy halves the risk of developing severe hypertension compared with placebo or no treatment

Risk of chronic hypertension if gestational hypertension (3)

• study evidence found that risk of chronic hypertension increased dramatically and rapidly in the years following delivery in women who developed gestational hypertension (aHR (adjusted Hazard Ratio) 6.03; 95% CI, 5.89-6.17) or pre-eclampsia (8.10; 7.88-8.33)

Reference:

• (1) NICE (June 2019). Hypertension in pregnancy - the management of hypertensive disorders during pregnancy
• (2) Ashworth D, Battersby C, Green M, Hardy P, McManus R J, Cluver C et al. Which antihypertensive treatment is better for mild to moderate hypertension in pregnancy? BMJ 2022; 376 :e066333 doi:10.1136/bmj-2021-066333
• (3) Boucheron P et al. Hypertensive disorders of pregnancy and onset of chronic hypertension in France: the nationwide CONCEPTION study, European Heart Journal, 2021;, ehab686,