OG12.1 | Hypertensive Disorders of Pregnancy — Summary & Reflection

KEY TAKEAWAYS

Hypertensive Disorders of Pregnancy — Key Takeaways

What: HDP is a spectrum including chronic hypertension, gestational hypertension, pre-eclampsia (± severe features), eclampsia, HELLP syndrome, and superimposed pre-eclampsia. The 20-week gestational boundary is definitional.

Diagnosis: Pre-eclampsia = BP ≥140/90 after 20 weeks + proteinuria OR end-organ dysfunction. Severe features include BP ≥160/110, platelets <100 × 10⁹/L, creatinine >97 µmol/L, elevated transaminases ×2, pulmonary oedema, or new unresponsive headache/visual disturbance. Eclampsia adds convulsions; HELLP adds haemolysis.

Pathophysiology: Defective trophoblast invasion → defective spiral-artery remodelling → placental ischaemia → elevated sFlt-1/reduced PlGF → endothelial dysfunction → vasospasm, proteinuria, thrombocytopaenia, multi-organ damage.

Investigations: CBC (platelets), LFT, RFT, uric acid, urine PCR, coagulation screen; fetal surveillance with CTG, ultrasound biometry, umbilical artery Doppler.

Management:
- Acute severe HTN (≥160/110): labetalol, hydralazine, or oral nifedipine.
- MgSO4 prophylaxis/treatment: Pritchard IM (4 g IV + 10 g IM loading; 5 g IM 4-hourly maintenance) or Zuspan IV (4 g IV loading; 1 g/h infusion). Monitor: knee jerk present, RR ≥12/min, urine output ≥30 mL/h. Antidote: calcium gluconate 1 g IV (10 mL of 10%).
- Eclampsia management: airway, lateral decubitus, MgSO4, antihypertensive, then delivery.
- Definitive treatment = delivery of the placenta.
- Contraindicated in HDP: ACE inhibitors/ARBs (fetal toxicity); ergometrine/methylergometrine (hypertensive crisis risk).

Prevention: Low-dose aspirin (75–150 mg/day before 16 weeks) in high-risk women; calcium supplementation (1.5–2 g/day elemental calcium) in low-calcium-intake populations.

REFLECT

Take a few minutes to apply Kolb's reflective cycle to your learning from this module:

Concrete Experience: Return to the opening clinical scenario — the 26-year-old primigravida at 34 weeks with severe headache, BP 172/110, proteinuria 3+, and generalised tonic-clonic convulsions. She has eclampsia with severe features.

Reflective Observation: What was your initial reaction? Did you know the MgSO4 loading dose before reading this module? Could you distinguish Pritchard from Zuspan, and when would you choose each? Did you know to contraindicate ergometrine in her subsequent third-stage management?

Abstract Conceptualisation: Construct the mental model: the same pathophysiological mechanism (sFlt-1/PlGF imbalance → endothelial dysfunction) explains every clinical feature of her presentation — the headache (cerebral vasospasm), the visual symptoms (retinal arteriolar spasm), the proteinuria (glomerular endotheliosis), the epigastric risk (hepatic involvement), and the convulsions (cerebral vasospasm + PRES). When you understand the mechanism, you don't have to memorise the features — you can derive them.

Active Experimentation: In your next antenatal ward posting, find a patient with pre-eclampsia. Ask the registrar or consultant to let you review her investigation chart — can you identify which features are present? Check whether she is on MgSO4, and if so, walk through the monitoring parameters yourself. Discuss with the team which antihypertensive was chosen and why. Connect what you see clinically to the framework you built today.