Hypertensive disorders of pregnancy

Hypertensive disorders of pregnancy

Hypertensive disorders of pregnancy

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Quick Overview

Hypertensive disorders complicate 10-15% of pregnancies and remain a leading cause of maternal/fetal morbidity. NICE NG133 stratifies management by severity: gestational hypertension, pre-eclampsia, and severe pre-eclampsia, each with distinct diagnostic thresholds and treatment escalation. Timely recognition, appropriate antihypertensive therapy, and judicious use of magnesium sulfate for seizure prophylaxis are critical to prevent maternal stroke, eclampsia, and perinatal compromise.

Core Facts & Concepts

📊 Diagnostic Thresholds

  • Gestational hypertension: BP ≥140/90 mmHg after 20 weeks without proteinuria/organ dysfunction
  • Pre-eclampsia: BP ≥140/90 mmHg PLUS proteinuria (≥300 mg/24h or PCR ≥30 mg/mmol) OR organ dysfunction
  • Severe pre-eclampsia: BP ≥160/110 mmHg OR severe organ/uteroplacental dysfunction

Figure 1: Fundoscopy showing bilateral retinal haemorrhages and cotton-wool spots in severe pre-eclampsia

🚩 Organ Dysfunction Markers

  • Acute kidney injury (creatinine ≥90 μmol/L)
  • Liver involvement (transaminases >70 IU/L ± RUQ pain)
  • Haematological: platelets <150×10⁹/L, DIC, haemolysis
  • Neurological: eclampsia, stroke, persistent headache/visual disturbance
  • Uteroplacental: fetal growth restriction, abnormal Doppler, stillbirth

💊 First-Line Antihypertensives (NICE NG133)

DrugStarting DoseMaximum DoseNotes
Labetalol100 mg BD PO800 mg TDSAvoid in asthma
Nifedipine MR10 mg BD PO40 mg BDUse modified-release
Methyldopa250 mg BD-TDS PO1 g TDSAvoid postpartum (depression risk)

Target BP: 135/85 mmHg (avoid over-treatment; maintain uteroplacental perfusion)

Problem-Solving Approach

Step-by-Step Management

  1. Confirm diagnosis: Repeat BP measurement after 30 min rest; quantify proteinuria (PCR or 24h urine)
  2. Assess severity: Bloods (FBC, U&E, LFT, urate), fetal monitoring (CTG, USS growth/Doppler)
  3. Initiate treatment if BP ≥140/90: Start labetalol/nifedipine/methyldopa (see table above)
  4. Severe features (BP ≥160/110): Admit; IV labetalol 20 mg bolus OR oral nifedipine 10 mg (repeat every 30 min PRN)
  5. Magnesium sulfate criteria: Severe pre-eclampsia with imminent/actual eclampsia OR during delivery if BP ≥160/110
    • Regimen: 4 g IV loading over 5-15 min, then 1 g/h infusion for 24h
    • Monitor: Respiratory rate ≥16/min, patellar reflexes, urine output ≥25 mL/h
  6. Delivery timing:
    • Severe pre-eclampsia: Consider delivery from 34 weeks (balance maternal/fetal risk)
    • Uncontrolled BP/organ dysfunction: Deliver urgently regardless of gestation
    • Gestational hypertension alone: Aim for 37-40 weeks

⚠️ Warning: Rapid BP reduction (target 135/85, NOT normotension) risks placental hypoperfusion and fetal compromise

Analysis Framework

Differential Diagnosis: Hypertension in Pregnancy

FeatureChronic HTNGestational HTNPre-eclampsiaSevere Pre-eclampsia
Onset<20 weeks≥20 weeks≥20 weeks≥20 weeks
ProteinuriaAbsentAbsentPresentPresent
Organ dysfunctionAbsentAbsentMay be presentAlways present
BP threshold≥140/90≥140/90≥140/90≥160/110
Risk of eclampsiaLowLowModerateHigh

🎯 Key Discriminators

  • Proteinuria distinguishes gestational HTN from pre-eclampsia
  • Severe BP/organ dysfunction mandates magnesium sulfate consideration
  • HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets): variant of severe pre-eclampsia requiring urgent delivery

Visual Aid

Key Points Summary

Diagnostic thresholds: Gestational HTN ≥140/90 (no proteinuria); pre-eclampsia ≥140/90 + proteinuria/organ dysfunction; severe ≥160/110 or organ involvement
First-line drugs: Labetalol 100 mg BD → 800 mg TDS, nifedipine MR 10 mg BD → 40 mg BD, methyldopa 250 mg BD-TDS → 1 g TDS
Target BP 135/85 mmHg (avoid over-treatment)
Magnesium sulfate: 4 g IV load + 1 g/h infusion for severe pre-eclampsia with imminent eclampsia or during delivery if BP ≥160/110
Delivery timing: Severe pre-eclampsia from 34 weeks; urgent delivery if uncontrolled BP/organ dysfunction
Monitor MgSO4: Respiratory rate ≥16/min, reflexes present, urine output ≥25 mL/h (toxicity antidote: calcium gluconate 10 mL 10% IV)
HELLP syndrome is severe pre-eclampsia variant requiring urgent delivery

Practice Questions: Hypertensive disorders of pregnancy

Test your understanding with these related questions

A 37-year-old woman at 28 weeks gestation presents with sudden onset dyspnea and chest pain. She has a history of previous DVT. D-dimer is elevated. What is the most appropriate anticoagulant if PE is confirmed?

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Flashcards: Hypertensive disorders of pregnancy

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The correct position for women who have a cord prolpase is _____

TAP TO REVEAL ANSWER

The correct position for women who have a cord prolpase is _____

on all fours, on knees and elbows

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