Chronic hypertension in pregnancy

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

Women with essential hypertension who become pregnant are at increased risk of

• accelerated hypertension in the third trimester
• superimposed pre-eclampsia
• intra-uterine growth restriction (IUGR)
• placental abruption
• premature delivery and stillbirth (2)

Occasionally secondary hypertension due to known causes (e.g. - endocrine tumors, renal artery stenosis, and renal disease) may occur in pregnancy.

Chronic Hypertension in pregnancy:

Existing antihypertensive treatment should be continued 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

Labetalol should be considered as initial treatment for 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 aspirin 75-150 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.

Antenatal appointments

In women with chronic hypertension, schedule additional antenatal appointments based on the individual needs of the woman and her baby. This may include:

• weekly appointments if hypertension is poorly controlled
• appointments every 2 to 4 weeks if hypertension is well-controlled

Timing of birth

Do not offer planned early birth before 37 weeks to women with chronic hypertension whose blood pressure is lower than 160/110 mmHg, with or without antihypertensive treatment, unless there are other medical indications

In women with chronic hypertension who have given birth:

• aim to keep blood pressure lower than 140/90 mmHg
• continue antihypertensive treatment, if required
• offer a review of antihypertensive treatment 2 weeks after the birth, with their GP or specialist

if a woman has taken methyldopa to treat chronic hypertension during pregnancy, stop within 2 days after the birth and change to an alternative antihypertensive treatment

Women with chronic hypertension should be offered a medical review 6-8 weeks after the birth with their GP or specialist as appropriate.

Reference:

• (1) NICE (June 2019). Hypertension in pregnancy - the management of hypertensive disorders during pregnancy
• (2) Society of obstetrics medicine of Australia and New Zealand. Guidelines for the management of hypertensive disorders of pregnancy