Obstetrics and Gynaecology: Antenatal, Intrapartum and Emergency Care
Obstetrics and gynaecology questions centre on hypertensive disorders, haemorrhage, contraception and gynaecological oncology. The examiner expects precise thresholds, drug regimens and contraindications.
Core rules
- Severe preeclampsia: blood pressure at least 160/110 mmHg, or symptoms, or platelets below 100,000, or renal or hepatic involvement. Magnesium sulphate is given for seizure prophylaxis, with delivery at 34 weeks or later after stabilisation.
- Magnesium toxicity progresses from loss of deep tendon reflexes to respiratory depression to cardiac arrest; calcium gluconate is the antidote.
- Postpartum haemorrhage is most often due to uterine atony; oxytocin is first line, and ergometrine is avoided in hypertension.
- Copper intrauterine device is effective emergency contraception up to 5 days after unprotected intercourse.
Worked example
A woman at 34 weeks has blood pressure 170/110 mmHg, 2+ proteinuria, platelets 90,000 and headache. This is preeclampsia with severe features. Start magnesium sulphate with a 4-6 g intravenous loading dose over 20 minutes and 1-2 g/h maintenance, control blood pressure with intravenous labetalol or hydralazine, and deliver after maternal stabilisation, which is the definitive treatment at this gestation.
Traps
- Monitoring magnesium by serum levels alone rather than by reflexes, respiratory rate and urine output.
- Using ergometrine for atonic haemorrhage in a hypertensive patient.
- Forgetting that combined oral contraceptives lose efficacy with enzyme-inducing drugs.