Pre-eclampsia and eclampsia
High BP after 20 weeks with protein or organ involvement. Treat BP of 160/110 or more, give magnesium for severe disease or fits, watch for toxicity, and plan delivery.
A 21-year-old in her first pregnancy, at 35 weeks, has a severe headache and "flashing lights". Her feet and face are swollen. BP 172/114 on repeat. Urine protein 3+. While you are taking blood, she has a fit.
What do you do now?
- Call the obstetric emergency teamSenior obstetrician, anaesthetist, midwife.
- Fitting? Protect the airwayLeft lateral position, oxygen, suction. Do not restrain.
- Magnesium sulfateFor eclampsia, and for severe pre-eclampsia. Loading dose then maintenance.
- Treat BP of 160/110 or moreWithin 1 hour. Oral labetalol, oral nifedipine (swallowed, never sublingual) or IV labetalol or hydralazine.
- BloodsCBC (platelets), LFTs, urea, creatinine, electrolytes, uric acid, clotting, group and save. Urine protein.
- Fluids: restrictAbout 80 mL/hour in total. Strict input and output chart, catheter.
- Check the babyCTG once the mother is stable.
- Plan deliveryOnce the mother is stable. Delivery is the cure.
- BP 160/110 or more
- A fit
- Severe headache or visual problems
- Upper abdominal pain, vomiting
- Low platelets, raised ALT, haemolysis
- Breathless or low SpO₂
- Eclampsia
- HELLP syndrome
- Placental abruption
- Stroke or PRES
- Pulmonary oedema
- Postpartum pre-eclampsia
| Pre-eclampsia | BP 140/90 or more after 20 weeks, plus protein in urine or organ involvement |
| Severe BP | 160/110 or more: treat within 1 hour |
| BP target | About 135/85 |
| Magnesium | For eclampsia and severe pre-eclampsia: Zuspan or Pritchard regimen (doses in the magnesium section) |
| Magnesium toxicity | Lost knee reflexes, RR below 12, low urine: stop magnesium, give calcium gluconate |
Check every dose against a current drug reference and your hospital protocol.
On this page
What it is
Pre-eclampsia is a disease of the placenta that affects the whole body: blood vessels, kidneys, liver, brain and clotting. It starts after 20 weeks of pregnancy and can appear up to 6 weeks after delivery. The only cure is delivery of the placenta.
New BP of 140/90 or more after 20 weeks, plus one or more of:
- Protein in the urine (protein:creatinine ratio 30 mg/mmol or more, or dipstick 2+ or more).
- Kidney involvement: creatinine 1 mg/dL (90 µmol/L) or more.
- Liver involvement: raised ALT or AST, with or without upper abdominal pain.
- Neurological: severe headache, visual problems, fits (eclampsia), stroke.
- Blood: platelets below 150,000/µL, haemolysis, clotting problems.
- Placenta: baby not growing, abnormal Doppler, stillbirth.
BP 160/110 or more, severe headache, visual disturbance, upper abdominal (epigastric or right upper quadrant) pain, vomiting, fits, platelets below 100,000/µL, rising creatinine or liver enzymes, pulmonary oedema, clonus.
HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets) is a severe form. The BP may be only mildly raised. Upper abdominal pain and vomiting can be mistaken for "gastritis".
Controlling the BP
- Target: about 135/85. Do not drop the BP suddenly: the baby depends on placental blood flow.
- Check BP every 15 minutes until stable, then every 30 minutes.
Magnesium sulfate
Magnesium prevents and treats eclamptic fits better than diazepam or phenytoin. Give it for eclampsia and for severe pre-eclampsia when delivery is planned or there are severe features.
- 4 g IV over 5–15 minutes
- Then 1 g/hour IV infusion
- For 24 hours after delivery or the last fit, whichever is later
- 4 g IV over 5–15 minutes, plus 10 g IM (5 g deep IM into each buttock)
- Then 5 g deep IM every 4 hours, alternating buttocks
- Common in Pakistan where pumps are limited
Check before each dose and at least hourly:
- Knee reflexes present.
- Breathing rate 12 or more per minute.
- Urine output at least 25–30 mL/hour (100 mL in 4 hours).
If reflexes are lost, breathing is below 12, or urine is low: stop the magnesium, call your senior, and check a magnesium level. If breathing is depressed, give calcium gluconate 10%, 10 mL IV over 10 minutes, and support the airway.
- Kidney injury: magnesium builds up. Reduce or stop maintenance doses on senior advice.
Fluids
- Restrict fluids: about 80 mL/hour in total (all drips and drugs included) unless there is ongoing loss such as bleeding.
- Strict fluid balance with a urinary catheter.
- These women develop pulmonary oedema easily: listen to the chest and watch SpO₂.
Delivery
- Delivery is the cure. Timing depends on the mother's condition and the gestation.
- Stabilise the mother first (BP control, magnesium), then deliver. Do not rush to theatre with an uncontrolled BP or during a fit.
- Steroids for the baby's lungs if under 35 weeks and time allows.
- Avoid ergometrine for the third stage. Use oxytocin.
After delivery
- BP often peaks 3–5 days after delivery. Continue BP checks.
- Continue magnesium for 24 hours after delivery or the last fit.
- Postpartum eclampsia can happen up to 6 weeks after birth. A fitting woman who delivered recently has eclampsia until proven otherwise.
- Switch to oral antihypertensives (for example enalapril, amlodipine or labetalol). Most are safe in breastfeeding.
- Next pregnancy: aspirin 75–150 mg at night from 12 weeks for women at high risk, and early booking.
Common mistakes
- Giving diazepam instead of magnesium for an eclamptic fit.
- Sublingual nifedipine.
- Running litres of fluid "for the kidneys".
- Forgetting to check reflexes and breathing before each magnesium dose.
- Calling epigastric pain in late pregnancy "gastritis" (HELLP).
- Stopping BP monitoring the day after delivery.
Frequently asked questions
What is the magnesium sulfate regimen for eclampsia?
Zuspan: 4 g IV over 5–15 minutes, then 1 g/hour IV for 24 hours. Pritchard: 4 g IV plus 10 g IM (5 g each buttock), then 5 g IM every 4 hours. Recurrent fits: another 2–4 g IV.
What are the signs of magnesium toxicity?
Loss of knee reflexes, breathing rate below 12 per minute, low urine output, and later heart block or cardiac arrest. Treatment is to stop the magnesium and give 10 mL of 10% calcium gluconate IV.
What BP needs urgent treatment in pre-eclampsia?
160/110 or more should be treated within an hour, aiming for about 135/85.
Can pre-eclampsia happen after delivery?
Yes, up to 6 weeks after delivery, with BP often highest 3–5 days after birth.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A woman at 35 weeks has an eclamptic fit. Which drug is first-line?
Answer: Magnesium sulfate. Magnesium sulfate: 4 g IV over 5–15 minutes, then maintenance, reduces recurrent fits and maternal death.
- Labetalol only: Doesn't stop fits.
- Diazepam: Magnesium is superior.
- Levetiracetam: Not first-line.
- Phenytoin: Inferior.
2. A woman on magnesium sulfate has absent knee reflexes and a respiratory rate of 10. What should be done?
Answer: Stop magnesium, give calcium. Loss of reflexes and respiratory depression indicate magnesium toxicity. Calcium gluconate reverses it.
- Continue and recheck in 1 hour: Dangerous.
- Increase magnesium: Toxicity.
- Give furosemide: Not the antidote.
- Give naloxone: Not opioid.
3. A woman at 36 weeks has upper abdominal pain, BP 146/94, platelets 70,000/µL and ALT 310. What is the diagnosis?
Answer: HELLP syndrome. Haemolysis, elevated liver enzymes and low platelets. Senior obstetrician, magnesium, BP control and delivery planning.
- Gallstones: Not with this pattern.
- Gestational thrombocytopenia: Doesn't explain liver enzymes and BP.
- Acute fatty liver of pregnancy: Usually with hypoglycaemia and coagulopathy.
- Viral hepatitis: Doesn't fit low platelets and hypertension.
4. A primigravida with chronic hypertension and diabetes books at 10 weeks. What should be started at 12 weeks to reduce pre-eclampsia risk?
Answer: Low-dose aspirin 75–150 mg. Women at high risk of pre-eclampsia (previous pre-eclampsia, chronic hypertension, CKD, diabetes, autoimmune disease/APS, multiple pregnancy) or ≥ 2 moderate risk factors should take low-dose aspirin (75–150 mg nightly) from 12 weeks (before 16) until 36 weeks. In low calcium intake populations (as in Pakistan), calcium supplementation (1.5–2 g/day) also reduces pre-eclampsia (WHO). Antioxidant vitamins and bed rest are ineffective.
- Calcium channel blocker for everyone: For BP control, not prevention.
- Vitamin C and E: Vitamins C and E do not prevent pre-eclampsia.
- Bed rest: Bed rest doesn’t prevent pre-eclampsia and raises VTE risk.
5. A woman at 36 weeks has a generalised seizure. BP is 170/115. After securing airway and left lateral position, what is given?
Answer: IV magnesium sulfate loading. Eclampsia: seizures with pre-eclampsia. ABC, left lateral tilt, oxygen; MgSO₄ 4 g IV over 5–20 min then 1 g/h for 24 h (or Pritchard IM regimen used widely in Pakistan); recurrent seizure → further 2 g. Control severe BP (labetalol/nifedipine/hydralazine). Deliver once stable (regardless of gestation). Monitor magnesium toxicity. MgSO₄ is superior to diazepam and phenytoin (Collaborative Eclampsia Trial).
- IV diazepam as first-line: Diazepam is inferior to MgSO₄.
- IV phenytoin: Phenytoin is inferior to MgSO₄.
- Oral nifedipine only: Nifedipine does not stop seizures.
6. What is the main underlying cause of pre-eclampsia?
Answer: Failed spiral artery remodelling. Normally, trophoblast converts spiral arteries into wide, low-resistance vessels. In pre-eclampsia this fails, the placenta becomes ischaemic and releases antiangiogenic factors (sFlt-1), causing widespread maternal endothelial dysfunction: hypertension, proteinuria, oedema, and in severe cases HELLP, eclampsia and DIC. Delivery of the placenta is the cure.
- Excess maternal salt intake: Not the cause.
- Primary maternal kidney disease: Not the cause (but a risk factor).
- Fetal growth restriction: Growth restriction is a consequence.
- Maternal infection: Not the cause.
7. A woman with severe pre-eclampsia has haemolysis, ALT 200 U/L and platelets 60 × 10⁹/L. What is the diagnosis and definitive treatment?
Answer: HELLP; stabilise and deliver. HELLP (haemolysis, elevated liver enzymes, low platelets) is a severe variant of pre-eclampsia with epigastric/right upper quadrant pain; risks include liver haematoma or rupture, DIC and abruption. Management: control BP, magnesium sulphate for seizure prophylaxis, correct coagulopathy, and delivery, the only definitive treatment.
- Acute fatty liver; observe: Hypoglycaemia, coagulopathy, not haemolysis predominantly.
- ITP; steroids only: No hypertension or haemolysis.
- TTP; plasma exchange only: Rare; neuro signs, ADAMTS13.
- Viral hepatitis; antivirals: Not this picture.
References and dose sources
- NICE NG133: Hypertension in pregnancy
- Magpie trial: magnesium sulfate in pre-eclampsia
- RCOG — Green-top guidelines
- Labetalol dosing: Drugs.com: Labetalol dosage (see also our labetalol dose page)
- Nifedipine dosing: Drugs.com: Nifedipine dosage (see also our nifedipine dose page)
- Hydralazine dosing: Drugs.com: Hydralazine dosage (see also our hydralazine dose page)
- Magnesium sulfate dosing: Drugs.com: Magnesium sulfate dosage (see also our magnesium sulfate dose page)
- Calcium gluconate dosing: Drugs.com: Calcium gluconate dosage (see also our calcium gluconate dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.