Background Information
Definition and Classifications
| Term | Definition |
|---|---|
| Chronic hypertension | Hypertension present or diagnosed before 20 weeks gestation |
| Gestational hypertension | New onset hypertension(≥140/90 mmHg) after 20 weeks gestation WITHOUT proteinuria |
| Pre-eclampsia | New onset hypertension (≥140/90 mmHg) after 20 weeks gestation AND 1 or more of the following new-onset conditions:
|
| HELLP syndrome | A serious complication associated with pre-eclampsia, characterised by:
|
| Eclampsia | Occurrence of seizure in a woman with pre-eclampsia (usually generalised tonic-clonic) |
Severe hypertension is defined as BP ≥160/110 mmHg, which typically requires urgent inpatient antihypertensive treatment (see Management below).
Epidemiology
Hypertensive disorders occur in 8-10% of al 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
The pathophysiology of pre-eclampsia is covered in detail as it is the most clinically distinct and exam-relevant.
No specific pathophysiological mechanisms apply for chronic hypertension and gestational hypertension. While HELLP syndrome and eclampsia are associated with pre-eclampsia, thus share a similar underlying 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-aniogentic 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).
| High risk factors |
|
| Moderate risk factors |
|
| Other risk factors |
|
Complications
| Condition | Complications |
|---|---|
| Chronic hypertension (in pregnancy) | Risk of superimposed pre-eclampsia (~25% women develops it)
Chronic hypertension is associated with increased risk of:
|
| Gestational hypertension | 40-50% risk of pre-eclampsia and increased risk of IUGR
Other complications:
|
| Pre-eclampsia | Pregnancy / neonatal associated complications:
Pre-eclampsia and eclampsia accounts for 4% of all UK maternal mortality. Causes include:
|
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:
| High risk factors |
|
| Moderate risk factors |
|
Preventive Therapy
Drug of choice: aspirin 75-150 mg PO OD
Timing: from 12 weeks of gestation and continue until birth
Apart from aspirin, NICE states NOT to recommend any of the following to prevent hypertensive disorders during pregnancy (unless they are indicated for other reasons):
- Other pharmacological agents (low molecular weight heparin, diuretics, progesterone, nitric oxide donors)
- Nutritional supplements (magnesium, folic acid, vitamin C and E, fish oils, algal oils, garlic)
- Salt-restricted diet
- Specific lifestyle changes (i.e. give the same advice as other healthy pregnant women)
Hypertensive Disorders
Chronic Hypertension
Change to Pre-Existing Treatment
The following anti-hypertensive medications should be stopped:
- ACE inhibitor and ARB
- Thiazide and thiazide-like diuretics
Calcium channel blockers are safe in pregnancy.
Most patients with chronic hypertension are likely to be taking a statin as well, statins should also be stopped prior to pregnancy.
Management
Blood pressure target: 135/85 mmHg
Offer additional anti-hypertensive treatment if BP ≥140/90 mmHg:
- 1st line: labetalol
- 2nd line: nifedipine
- 3rd line: methyldopa
As mentioned above, chronic hypertension is an indication for pre-eclampsia prevention, these patients should take aspirin 75-150 mg daily from 12 weeks until birth.
Timing of Birth
Chronic hypertension alone is NOT an indication for early birth before 37 weeks.
Gestational Hypertension
Admission Criteria
Admit if systolic BP ≥160 mmHg and/or diastolic BP ≥110 mmHg (i.e. severe hypertension)
Management
Blood pressure target: 135/85 mmHg
Offer anti-hypertensive treatment if BP ≥140/90 mmHg:
- 1st line: labetalol
- 2nd line: nifedipine
- 3rd line: methyldopa
Note that gestational hypertension alone is NOT an indication to take aspirin daily for pre-eclampsia prevention.
Timing of Birth
Gestational hypertension alone is NOT an indication for early birth before 37 weeks.
Post-Natal Management
- If methydopa is started → stop within 2 days and change to an alternative
- Monitor blood pressure
- Daily for first 2 days
- At least once between day 3-5
- Review 6-8 weeks after birth (if remaining on anti-hypertensive treatment, review 2 weeks after)
For those who did not take antihypertensive treatment and have given birth, start antihypertensive treatment if BP ≥150/100 mmHg.
Pre-Eclampsia
Testing
Offer PLFG-based testing (maternal blood test) at 20-36+6 weeks to exclude pre-eclampsia, if suspected
- Low (marked decrease) → high risk of pre-eclampsia
- High → low risk (consider alternative diagnosis)
Management
Admission Criteria
Offer hospital admission if any of the following:
- Systolic BP ≥160 mmHg
- Abnormal blood tests
- ↑ Creatinine (≥90 mmol/L)
- ↑ ALT (2x of upper limit normal range / >70 IU/L)
- ↓ Platelet (<150,000)
- Signs of impending pulmonary oedema
- Signs of severe pre-eclampsia
- Suspected fetal compromise
- Signs of impending eclampsia
Choice of Anti-Hypertensive Therapy
Same as gestational hypertension:
- Blood pressure target: 135/85 mmHg
- Offer anti-hypertensive treatment if BP ≥140/90 mmHg:
- 1st line: labetalol
- 2nd line: nifedipine
- 3rd line: methyldopa
Magnesium Therapy
Consider giving magnesium sulfate (for eclampsia prophylaxis) if at least 1 of the following severe pre-eclampsia features is present:
- Ongoing or recurring severe headaches
- Visual scotomata
- Nausea or vomiting
- Epigastric pain
- Oliguria and severe hypertension (≥160/110 mmHg)
- Progressive deterioration in laboratory blood tests (e.g. rising creatinine or liver transaminases, or falling platelet count)
Timing of Birth
Once ≥37 weeks of gestation is reached, delivery should be planned within 24–48 hours.
Only consider early 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
Fetal Monitoring
Tests
Tests for fetal monitoring:
- Ultrasound – assess fetal growth and amniotic fluid volume assessment
- Umbilical artery doppler
- Cardiotocography – assess fetal wellbeing
Monitoring Frequency
| Hypertensive disorder | Test | Frequency |
|---|---|---|
| Chronic hypertension | Ultrasound | At 28, 32, 36 weeks |
| Umbilical artery doppler | ||
| Gestational hypertension | Ultrasound | At diagnosis Then, repeat every 2-4 weeks (if normal) |
| Umbilical artery doppler | ||
| Pre-eclampsia / severe gestational hypertension (≥160/110 mmHg) | Cardiotocography | At diagnosis (no need for routine repeat after) |
| Ultrasound | At diagnosis, Then every 2 weeks |
|
| Umbilical artery doppler |
Apart from pre-eclampsia / severe gestational hypertension, there is no need for routine cardiotocography, unless clinically indicated.
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 snydorme 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 managaement is prompt delivery, regardless of gestational age [Ref]
Maternal stabilisation is important prior to delivery, 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).
Do NOT use diazepam, phenytoin or other anticonvulsants as an alternative to magnesium sulfate in women with eclampsia.
Monitoring for clinical signs of magnesium toxicity in the mother at least 4 hourly:
- Deep tendon reflex (reduced deep tendon reflex) – the earliest and most sensitive indicator
- Blood pressure (hypotension)
- Respiratory rate (respiratory depression)
Management of magnesium toxicity: stop the magnesium infusion + IV calcium gluconate (antidote)
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)
Post-Natal Management
Monitoring and Follow-Up
- Monitor blood pressure
- Gestational hypertension → daily during day 1-3
- Pre-eclampsia → 4 times a day while inpatient
- Review 6-8 weeks after birth
Choice of Antihypertensives
If methyldopa is started during pregnancy → stop it within 2 days and change back to conventional anti-hypertensive drugs, see below for choice.
Breastfeeding or Planning to Breastfeed
Breastfeeding is NOT a contraindication for anti-hypertensive therapy. The following is recommended for hypertensive patients:
- 1st line:
- Enalapril
- If black Afro-Caribbean → nifedipine / amlodipine
- 2nd line:
- Enalapril + nifedipine / amlodipine
- 3rd line:
- Add atenolol / labetalol to enalapril + nifedipine / amlodipine, or
- Swap 1 medication to atenolol / labetalol
Although NOT absolutely contraindicated, NICE recommends AVOIDING diuretics and ARBs to treat hypertension in the postnatal period during breastfeeding / expressing milk.
Not Breastfeeding or Planning to Breastfeed
Hypertension is treated as per standard NICE hypertension guidelines
References