Hypertension in Pregnancy

This updated UKMLA guide covers chronic hypertension, gestational hypertension, pre-eclampsia, eclampsia and HELLP syndrome.

Definition and Classifications

Epidemiology

Hypertensive disorders occur in 8-10% of all pregnancies

• Gestational hypertension rates range from 4.2-7.9%
• Pre-eclampsia rates range from 1.5–7.7% but depend on parity:
  • 4.1% in 1st pregnancy
  • 1.7% in second pregnancy
• HELLP and eclampsia are rare but serious

Pathophysiology

Core concept: abnormal placentation

• Normal pregnancy: trophoblasts invade the spiral arteries → remodel them into wide, low-resistance vessels → adequate uteroplacental blood flow
• Pre-eclampsia: failed invasion → spiral arteries remain narrow and high-resistance → placental hypoperfusion (insufficiency)

Consequences of placental hypoperfusion

• Hypoperfused placenta releases anti-angiogenic factors and reduces pro-angiogenetic factors (e.g. placental growth factor)
• This causes widespread maternal endothelial damage → hypertension, proteinuria, multi-organ dysfunction

Risk Factors

Gestational Hypertension Risk Factors

• Nulliparity
• Multiple pregnancy
• Black ethnicity
• Maternal obesity
• Maternal type 1 diabetes

Pre-Eclampsia Risk Factors

These risk factors are important, as it guides preventive therapy (see below for more details).

Complications

Short-Term Implications

Long-Term Implications

Increased risk of:

• Chronic hypertension
• Stroke
• Cardiovascular events (e.g. ischaemic heart disease)
• End-stage kidney disease

Overall risk of hypertensive disorders of pregnancy recurrence is ~1 in 5

Hypertensive disorders of pregnancy are also associated with increased risk of:

• Type 2 diabetes
• Hyperlipidaemia
• Heart failure
• Atrial fibrillation
• Vascular dementia
• VTE

Pre-Eclampsia Prevention

Indications

Preventive therapy is indicated if there are:

• 1 or more high-risk factors, or
• 2 or more moderate risk factors

Pre-eclampsia risk factors:

Preventive Therapy

Drug of choice: aspirin 75-150 mg PO OD

Timing: start at 12 weeks of gestation and continue until birth

Initial Assessment and Diagnosis

Any pregnant patients who are >20 weeks of gestation presenting with high blood pressure +/- other symptoms (i.e. hypertensive disorder of pregnancy), share the same initial assessment principles, which determine which hypertensive disorder the patient has and whether the patient needs urgent admission.

Maternal Assessment

Immediate step: assess maternal stability

• If unstable → refer to hospital (if patient is in primary care) or call for senior obstetric help + perform A-E (in secondary care)
• If stable → perform a full assessment in a secondary care setting

A full assessment should include:

Diagnosis of Hypertensive Disorder in Pregnancy

Fetal Assessment

Immediate fetal assessment is indicated for the following situations:

For ongoing fetal assessment, see the management section below.

Management

Chronic Hypertension

Change to Pre-Existing Treatment

The following anti-hypertensive medications should be stopped immediately:

• ACE inhibitor and ARB (due to risk of congenital abnormalities)
• Thiazide and thiazide-like diuretics (due to risk of congenital abnormalities and neonatal complications)

Calcium channel blockers are safe in pregnancy.

Antenatal Management

Also schedule additional antenatal appointments based on the individual’s need, NICE recommends:

• Weekly appointment if hypertension is poorly controlled
• Every 2-4 weekly appointments if hypertension is well controlled

Fetal Monitoring

Routine fetal monitoring with the following is recommended at 28, 32 and 36 weeks:

• Ultrasound assessment of fetal growth and amniotic fluid volume
• Umbilical artery Doppler

Timing of Birth

Chronic hypertension alone is NOT an indication for planned preterm birth if BP is controlled <160/110 mmHg and there are no other maternal or fetal concerns.

After 37 weeks, timing of birth should be individualised and agreed between the woman and a senior obstetrician, taking into account BP control, antihypertensive use, maternal condition, fetal growth and fetal surveillance.

Postpartum Management

• If methydopa is started → stop within 2 days and change to an alternative drug
• Monitor blood pressure
  • Daily for the first 2 days
  • At least once between days 3-5
• Review 6-8 weeks after birth with GP or specialist
  • If the patient remains on anti-hypertensive treatment, review 2 weeks after

Gestational Hypertension

Admit to hospital if systolic BP ≥160 mmHg and/or diastolic BP ≥110 mmHg (i.e. severe hypertension)

• Offer anti-hypertensive treatment (target: <135/85 mmHg)
  • 1st line: labetalol (avoid in asthma)
  • 2nd line: nifedipine
  • 3rd line: methyldopa
• Monitor the following regularly
  • Blood pressure (every 15-30 min until BP is <160/110 mmHg)
  • Proteinuria (daily urine dipstick while admitted)
  • FBC, LFT, U&E weekly

Antenatal Management

Offer hospital admission if there is severe hypertension (systolic BP ≥160 mmHg and/or diastolic BP ≥110 mmHg)

Maternal management:

Maternal monitoring:

Fetal Monitoring

Routine fetal monitoring with the following is recommended at diagnosis (and to be repeated every 2-4 weeks, if normal):

• Ultrasound assessment of fetal growth and amniotic fluid volume
• Umbilical artery Doppler

Offer fetal heart auscultation at every antenatal appointment

Timing of Birth

Gestational hypertension alone is NOT an indication for planned preterm birth if BP is controlled <160/110 mmHg and there are no other maternal or fetal concerns.

After 37 weeks, timing of birth should be individualised and agreed between the woman and a senior obstetrician, taking into account BP control, antihypertensive use, maternal condition, fetal growth and fetal surveillance.

Post-Natal Management

• If methydopa is started → stop within 2 days and change to an alternative drug
• Continue antihypertensive treatment if required; reduce if BP falls <130/80 mmHg
• Monitor blood pressure
  • Daily for the first 2 days
  • At least once between days 3-5
• Review 6-8 weeks after birth with GP or specialist
  • If the patient remains on anti-hypertensive treatment, review 2 weeks after

For those who did not take antihypertensive treatment, start treatment if BP is ≥150/100 mmHg

Pre-Eclampsia

Excluding Pre-Eclampsia

Offer PLFG-based testing (maternal blood test) at 20-36⁺⁶ weeks to exclude pre-eclampsia, if suspected (e.g. in those with chronic hypertension or gestational hypertension)

• Low (marked decrease) → high risk of pre-eclampsia
• High → low risk (consider alternative diagnosis)

Antenatal Management

Offer hospital admission for surveillance and interventions if ANY of the following:

• Systolic BP ≥160 mmHg (sustained)
• New and persistent:
  • ↑ Creatinine (≥90 mmol/L), or
  • ↑ ALT (2x of upper limit normal range / >70 IU/L), or
  • ↓ Platelet (<150,000)
• Signs of impending pulmonary oedema
• Signs of severe pre-eclampsia
• Signs of impending eclampsia
• Suspected fetal compromise (e.g. abnormal CTG)

Maternal management:

Maternal monitoring:

Fetal Monitoring

Perform a CTG at diagnosis

• Repeat CTG is the patient reports a change in fetal movement, or vaginal bleeding / abdominal pain occurs, or if there is deterioration in maternal condition

Routine fetal monitoring with the following is recommended at diagnosis and repeated every 2 weeks:

• Ultrasound assessment of fetal growth and amniotic fluid volume
• Umbilical artery Doppler

Offer fetal heart auscultation at every antenatal appointment

Timing of Birth

Consider planned pre-term birth (before 37 weeks) if ANY of the following:

• Inability to control BP despite 3 classes of medication
• SpO₂ <90%
• Progressive deterioration in liver function / renal function / haemolysis / platelet count
• Ongoing neurological features (e.g. severe headache, repeated visual disturbances, eclampsia)
• Placental abruption
• Reversed end-diastolic flow in umbilical artery doppler / non-reassuring CTG / still birth

The decision should be made with senior obstetric and anaesthetic input.

From 37 weeks onwards, initiate birth within 24-48 hours

• Pre-eclampsia alone does not determine the mode of birth – i.e. between labour induction (vaginal delivery) vs elective caesarean delivery
• See the Vaginal Delivery and Caesarean Section article for more information

Postnatal Management

For all patients:

• If methydopa is started → stop within 2 days and change to an alternative drug
• Follow up with GP or specialist 6-8 weeks after the birth
  • If the patient remains on anti-hypertensive treatment, review 2 weeks after

HELLP Syndrome

Clinical Features

HELLP syndrome typically presents in the 3rd trimester, but 20-30% cases occur within 48 hours postpartum

Most common presenting symptoms: ^[Ref1][Ref2]

• RUQ or epigastric pain (up to 90%)
• Generalised malaise (up to 90%)
• Nausea and vomiting
• Headache
• Weight gain

Investigation and Diagnosis

HELLP syndrome is diagnosed based on the presence of ALL 3 laboratory components: ^[Ref]

• Haemolysis (indicated by raised LDH)
• Elevated liver enzymes (AST or ALT >2x upper limit of normal)
• Thrombocytopaenia

Other haemolysis findings include:

• Coombs-negative haemolytic anaemia
• Decreased haptoglobin
• Unconjugated hyperbilirubinaemia

Management

The only definitive management is prompt delivery, regardless of gestational age ^[Ref]

Maternal stabilisation is important prior to delivery, and it is often achieved via: ^[Ref]

• Magnesium sulfate – for eclampsia prophylaxis
• Antihypertensive therapy – for BP control
• Corticosteroids – for fetal lung maturation in pregnancies <34 weeks

Eclampsia

Seizure Management

Give IV magnesium sulfate immediately if eclampsia develops (i.e. if a seizure develops in someone with pre-eclampsia).

Anti-Hypertensive Treatment

Treat severe hypertension (≥160/110 mmHg) with any of the following:

• Labetalol (oral / IV)
• Oral nifedipine
• IV hydralazine

Definitive Management

Definitive management:

• First, stabilise the mother (by treating the seizure and hypertension)
• Then, deliver the baby (once the mother is stabilised)

References