Obstetric Complications and High-Risk Pregnancy
Domain 2 - Obstetric Complications and High-Risk Pregnancy
This domain covers hypertensive disease, diabetes, preterm labour, isoimmunisation and medical disorders in pregnancy. The exam tests thresholds, timing of delivery, and drug safety - the exact numbers that separate a safe plan from a dangerous one.
Core rules
- Preeclampsia: BP ≥140/90 on two occasions 4 hours apart at ≥20 weeks plus proteinuria ≥300 mg/24 h or any organ dysfunction (platelets <100,000, creatinine >1.1 mg/dL, transaminases twice normal, pulmonary oedema, visual/cerebral symptoms).
- Severe features: BP ≥160/110, thrombocytopenia, HELLP, symptoms. Delivery at ≥37 weeks without severe features; at 34 weeks with severe features after steroids and stabilisation; immediately for eclampsia or HELLP.
- Magnesium sulfate: Pritchard 4 g IV + 10 g IM, then 5 g IM every 4 hours; Zuspan 4 g IV over 20 minutes then 1 g/hour. Continue 24 hours postpartum.
- Antihypertensives: nifedipine, labetalol, methyldopa. Never ACE inhibitors, ARBs or atenolol.
- Aspirin 81–150 mg from 12–16 weeks for high-risk women.
- Gestational diabetes: 75 g OGTT at 24–28 weeks; targets fasting <95 mg/dL and 2-hour <120 mg/dL; insulin if diet fails.
- Preterm labour <37 weeks: tocolysis buys 48 hours for dexamethasone 6 mg IM four doses.
Worked example
A 32-year-old at 34 weeks has BP 168/112, 3+ proteinuria and platelets 90,000. This is preeclampsia with severe features. Plan: admit, magnesium sulfate, nifedipine to keep BP <160/110, dexamethasone, strict fluid balance, and caesarean or induction after 24–48 hours of stabilisation - not emergency delivery in the next hour unless she deteriorates.
Traps
Diagnosing preeclampsia before 20 weeks (think molar pregnancy); giving magnesium without checking reflexes, respiratory rate and urine output; stopping magnesium at delivery; overloading with fluid; using a single high BP reading.