PassFinals
Women's Health

Pre-eclampsia

A placental disease of the second half of pregnancy: shallow placentation injures the maternal endothelium, so new hypertension after 20 weeks arrives with kidney, liver, brain, platelet or fetal damage.

In a nutshell

New hypertension after 20 weeks plus proteinuria, maternal organ dysfunction or uteroplacental dysfunction. Treat above 140/90 mmHg with labetalol, give magnesium sulfate 4 g intravenously for seizures, restrict fluid to 80 mL/hour, and plan birth with a senior obstetrician.

Classic presentation

A 41-year-old primigravida at 34 weeks has a blood pressure of 168/112 mmHg, 2+ proteinuria, a frontal headache, flashing lights and right upper quadrant pain.

Key points

  • HELLP syndrome is Haemolysis, Elevated Liver enzymes and Low Platelets. Do not give dexamethasone or betamethasone to treat it.
  • Eclampsia, HELLP, haemorrhage, severe oliguria or intravenous antihypertensives means level 2 critical care.
  • Recurrence in a future pregnancy is about 1 in 6 after pre-eclampsia, and about 1 in 3 if the birth was at 28 to 34 weeks.
  • Pre-eclampsia raises later stroke risk about 2 to 3 times and later hypertension 2 to 5 times.
  • Eclampsia is rare, about 1 in 3000 UK pregnancies; severe disease about 1 in 200.
  • Magnesium sulfate for longer than 5 to 7 days in pregnancy risks neonatal hypocalcaemia and skeletal effects.
  • Urine dipstick at 6 to 8 weeks; 1+ or more needs a kidney review at 3 months.

First-line investigation

Blood pressure plus urine PCR (protein:creatinine ratio) or ACR (albumin:creatinine ratio), with FBC, U&E and LFT to look for organ dysfunction.

Management

Recognise and stabilise severe disease

  • Sustained systolic 160 mmHg or higher, an eclamptic fit, clonus, pulmonary oedema or fetal compromise: admit and call the obstetric registrar.1
  • Severe hypertension: labetalol 50 mg intravenously over at least 1 minute, repeatable every 5 minutes to 200 mg; or hydralazine 5 to 10 mg slowly intravenously.1,12,13
  • Eclamptic fit: magnesium sulfate 4 g intravenously over 5 to 15 minutes, then 1 g/hour for 24 hours after the last fit. Not diazepam, not phenytoin.1,14

Confirm the diagnosis

  • Quantify proteinuria: PCR 30 mg/mmol or more, or ACR 8 mg/mmol or more. Not needed if organ or uteroplacental dysfunction is present.1
  • Bloods: creatinine 90 micromol/litre or more, transaminases over 40 IU/litre, or platelets below 150,000/microlitre each satisfy the organ criterion.1
  • Fetal ultrasound, umbilical artery Doppler and cardiotocography (CTG) at diagnosis. PLGF-based blood test once, between 20 and 36+6 weeks.3,4

Control blood pressure

  • Treat above 140/90 mmHg, target 135/85 mmHg or less. Labetalol 100 mg orally twice daily, increased weekly, maximum 2400 mg daily.1,5,6
  • If unsuitable: modified-release nifedipine 10 mg every 12 hours up to 40 mg every 12 hours, then methyldopa 250 mg two or three times daily.7,8,9,10
  • Stop ACE (angiotensin-converting enzyme) inhibitors and ARBs (angiotensin II receptor blockers), avoid thiazides: fetal renal damage, oligohydramnios, skull defects.1,11

Seizure prophylaxis, toxicity and fluids

  • Magnesium sulfate if birth is planned within 24 hours, or with severe headache, scotomata, vomiting, epigastric pain, oliguria with severe hypertension or worsening bloods.1
  • Monitor respiratory rate (above 16 per minute), urine output (above 25 mL/hour) and patellar reflexes every 4 hours.16,15
  • Antidote: calcium gluconate 10%, 10 to 20 mL slowly intravenously over 10 minutes (2.23 to 4.46 mmol calcium).15,17
  • Restrict maintenance fluid to 80 mL/hour. No boluses for oliguria, no preload before an epidural, unless starting intravenous hydralazine.1

Plan birth

  • Before 37 weeks: surveillance unless a threshold is crossed. From 37+0 weeks: initiate birth within 24 to 48 hours.1
  • Before 34 weeks add antenatal corticosteroids and magnesium sulfate 4 g intravenously over 15 minutes then 1 g/hour, for fetal neuroprotection.1,16

Prevent it next time

  • Aspirin 75 mg to 150 mg once daily from 12 weeks until birth: one high-risk factor, or more than one moderate-risk factor.1,18
  • High risk: previous hypertensive pregnancy, chronic kidney disease, autoimmune disease, type 1 or type 2 diabetes, chronic hypertension.1
  • Moderate risk: nulliparity, age 40 or over, pregnancy interval over 10 years, BMI 35 kg/m2 or more, family history, multi-fetal pregnancy.1

After the birth

  • Blood pressure four times daily as an inpatient. If untreated antenatally, start at 150/100 mmHg or higher. Stop methyldopa within 2 days.1,8
  • Enalapril is the postnatal first choice; nifedipine or amlodipine for women of black African or Caribbean family origin. Avoid diuretics and ARBs while breastfeeding.1
  • Platelets, transaminases and creatinine at 48 to 72 hours. Review at 2 weeks if still treated, everyone at 6 to 8 weeks.1

Exam traps

  • Proteinuria is not required. New hypertension plus low platelets, raised transaminases or growth restriction is pre-eclampsia.
  • Magnesium sulfate is an anticonvulsant, not an antihypertensive. It will not bring the blood pressure down.
  • Never bolus fluid for oliguria. Restrict to 80 mL/hour; chasing urine output floods the lungs.
  • Liver thresholds differ: transaminases over 40 IU/litre are diagnostic, alanine transaminase over 70 IU/litre triggers admission.
  • Placental growth factor (PLGF)-based testing rules pre-eclampsia in or out. It must never decide on early birth.
  • Birth removes the placenta, not the risk: hypertension, HELLP and eclampsia can all appear afterwards.
  • Methyldopa is stopped within 2 days of birth and switched, though it was fine antenatally.

Illustrations

Spiral-artery remodelling in normal pregnancy and pre-eclampsiaComparative diagram of effective trophoblast-associated spiral-artery remodelling in normal pregnancy and shallow, high-resistance remodelling associated with pre-eclampsia.PassFinals · original
Placental signalling and maternal endothelial dysfunctionSchematic showing placental factors contributing to maternal vascular dysfunction, with kidney, liver, brain, lungs and uteroplacental circulation as the clinically important affected systems.PassFinals · original
Placental vasculopathy in pre-eclampsiaHistology showing decidual vasculopathy of uteroplacental vessels in pre-eclampsia; use alongside, not instead of, the current clinical diagnostic criteria.Nephron, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE NG133: Hypertension in pregnancy: diagnosis and management (NG133 recommendations 1.1 to 1.10, tables 1 to 6 and terms used in this guideline)Published 25 Jun 2019 | Updated 17 Apr 2023
  2. Royal College of Obstetricians and Gynaecologists: Pre-eclampsia (patient information) (Prevalence, symptoms and postnatal onset)Updated 1 May 2026
  3. NICE HTG630: PLGF-based testing to help diagnose suspected preterm pre-eclampsia (HTG630 recommendations 1.1, 1.4 and 1.5)Published 27 Jul 2022
  4. NICE NG133: Update information (NG133 April 2023 amendment aligning PLGF-based testing with HTG630)Published 25 Jun 2019 | Updated 17 Apr 2023
  5. BNF: Labetalol hydrochloride (BNF monograph for prescribing detail, monitoring and cautions)
  6. Labetalol 100 mg film-coated tablets: summary of product characteristics (Section 4.2, hypertension in pregnancy oral dosing)Updated 31 Jul 2026
  7. BNF: Nifedipine (BNF monograph for prescribing detail and preparation-specific cautions)
  8. BNF: Methyldopa (BNF monograph for prescribing detail and cautions)
  9. Nifedipress MR 20 modified-release tablets: summary of product characteristics (Section 4.2, modified-release nifedipine dosing in hypertension)Updated 23 Jul 2026
  10. Methyldopa tablets 250 mg: summary of product characteristics (Section 4.2, adult dosing and maximum daily dose)Updated 10 Nov 2022
  11. MHRA (Medicines and Healthcare products Regulatory Agency) Drug Safety Update: ACE inhibitors and angiotensin II receptor antagonists, not for use in pregnancy (Fetal renal dysfunction, oligohydramnios, neonatal anuria and skull ossification defects)Published 17 May 2019
  12. Labetalol hydrochloride 5 mg/mL solution for injection: summary of product characteristics (Section 4.2, bolus and infusion dosing in severe hypertension of pregnancy)Updated 21 Jul 2023
  13. Hydralazine 20 mg powder for solution for injection: summary of product characteristics (Sections 4.1 and 4.2, hypertensive emergencies of pre-eclampsia)Updated 9 Sept 2024
  14. BNF: Magnesium sulfate (BNF monograph for prescribing detail, monitoring and toxicity)
  15. Magnesium sulfate 50% w/v solution for injection: summary of product characteristics (Sections 4.2 and 4.9, eclampsia regimen, monitoring thresholds and antidote)Updated 21 Oct 2019
  16. NICE NG25: Preterm labour and birth (NG25 recommendations 1.9.2, 1.10.4, 1.10.5 and 1.10.6)Published 20 Nov 2015 | Updated 10 Jun 2022
  17. Calcium gluconate 10% solution for injection or infusion BP: summary of product characteristics (Section 4.2, 10 to 20 mL delivers 2.23 to 4.46 mmol of calcium over 10 minutes)
  18. BNF: Aspirin (BNF monograph for prescribing detail and cautions)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.