Obstetrics
The Obstetrics domain tests applied decision-making across antenatal care, labour, and the puerperium, with emphasis on hypertensive disease, haemorrhage, fetal surveillance, and operative obstetrics. Questions often present a timed clinical scenario and ask for the next step, so link definitions to action thresholds.
Core rules and thresholds
- Pre-eclampsia: new hypertension ≥140/90 after 20 weeks plus proteinuria or maternal organ dysfunction. Severe features include ≥160/110, platelets <100 ×10^9/L, ALT/AST >2× upper limit, creatinine >97 µmol/L (1.1 mg/dL), pulmonary oedema, or cerebral/visual symptoms.
- Magnesium sulfate is indicated for eclampsia and severe pre-eclampsia: 4 g IV loading over 20 minutes, then 1 g/h; monitor patellar reflex, respiratory rate, and urine output; calcium gluconate is the antidote.
- Postpartum haemorrhage: give tranexamic acid 1 g IV within 3 hours of birth, repeat once at 30 minutes if bleeding continues; escalate uterotonics (oxytocin, ergometrine, carboprost, misoprostol) and use balloon tamponade or surgery for refractory cases.
- CTG: classify by baseline, variability, accelerations, and decelerations; late decelerations suggest uteroplacental insufficiency, variable decelerations suggest cord compression, and a prolonged deceleration >3 minutes requires urgent review and often expedited delivery.
Worked example
A 33-year-old at 33+2 weeks has BP 162/108, 3+ proteinuria, platelets 88, and ALT 130. This is severe pre-eclampsia. Admit, secure IV access, start magnesium sulfate, treat BP with labetalol or nifedipine, give antenatal corticosteroids, and plan delivery after stabilization and steroid benefit; do not delay delivery for fetal maturity if maternal condition deteriorates. Avoid ergometrine postpartum because it raises BP.
Traps
- Diagnosing pre-eclampsia without confirming proteinuria or organ dysfunction.
- Missing that a normal platelet count does not exclude severe disease.
- Giving magnesium sulfate without monitoring for toxicity.
- Attributing fetal bradycardia to “sleep” without checking maternal pulse and position.