Vasa praevia — structured oral station (12 minutes)

Opening prompt — "What does this report show, and how worried are you?"

Model response — classify, quantify, then escalate: ^[2][4]

• "This is vasa praevia. The vessel bridges the lobes of a bilobed placenta and crosses the internal os, so it is type 2. Pulsed-wave Doppler at the fetal heart rate confirms the vessel is fetal rather than a maternal cervical vessel."^[2][6]
• "I am very worried, and specifically more worried than I would be in a singleton. In the systematic review of deaths despite prenatal diagnosis, perinatal mortality was 9.2% in twins versus 0.2% in singletons, and twins accounted for 80% of overall mortality despite being under 10% of births."^[4]
• "She also has three additional risk factors for an unscheduled birth: twins, a cervical length of 24 mm, and a 90-minute travel time. Every perinatal death in that review occurred with an unscheduled delivery."^[4]

Examiner is listening for: the type named correctly, proof that the vessel is fetal, and an explicit statement that twins change the risk. ^[2][4]

Probe 1 — "How do you know this is real and not a maternal vessel?"

• "Transvaginal ultrasound with colour Doppler, and confirmation on pulsed-wave Doppler that the waveform is arterial at the fetal heart rate. That is how you exclude a maternal cervical or uterine vessel, a funic presentation, or a chorionic plate vessel not actually over the os."^[6][3]
• "In the systematic review, transvaginal colour Doppler in the second trimester detected all cases in the two prospective studies, with a specificity of 99.0 to 99.8%. It is a very good test in the right hands."^[6]

Probe 2 — "Would you admit her? Defend your answer."

This is the highest-yield probe in the station because there is no single right answer, only a defensible one. ^[3][10]

• Start with the guidance: "The international consensus says outpatient management is reasonable for an asymptomatic patient without risk factors for preterm birth, and the panel reached no agreement on routine hospitalisation. National guidelines also differ from each other on this point."^[3][10]
• Then individualise: "But this woman is not that patient. She has twins, a cervix of 24 mm, and lives 90 minutes away. I would recommend admission — I would aim for around 30 to 32 weeks, or sooner if the cervix shortens or she has any bleeding or contractions."^[4][3]
• Then justify with data: "In the systematic review, a policy of routine hospitalisation was associated with less neonatal transfusion, 0.9% versus 6.0%, and a reduction in twin mortality from 25% to 0%. In twins specifically, the evidence for admission is much stronger than in singletons."^[4]
• Close with the trade-off named: "Admission has real costs — separation from her other child, weeks in hospital, psychological burden. I would discuss those openly and agree the plan with her rather than impose it."^[3][10]

Probe 3 — "When will you deliver, and how?"

• "Caesarean, planned, before labour and before the membranes rupture. There is no vaginal-birth pathway."^[1][3]
• "In an uncomplicated singleton I would aim for 35 to 36 weeks, supported by the consensus window of 35 to 37 weeks and by the meta-analysis showing complications fall to 36 weeks — 0% perinatal death, 5.3% respiratory distress, 2.9% neonatal transfusion at that gestation."^[7][3]
• "For twins with a short cervix I would deliver earlier — around 34 weeks — because the driver of death is unscheduled birth, and twins are the group in whom that happens and kills."^[4][7]
• "Corticosteroids timed to the planned date, two neonatal teams and two cots, and the vessel position mapped so the uterine incision avoids it."^[1][3]

Probe 4 — the deterioration. "At 33 weeks she has ruptured membranes, heavy fresh vaginal bleeding, and the leading twin's heart rate is 60 bpm. Her observations are normal. Go."

Speak in short imperative sentences. The examiner is timing you. ^[1][5]

• "This is a ruptured vasa praevia. Category-1 caesarean now. Pull the emergency buzzer, call the obstetric consultant, the anaesthetist, and two neonatal teams."
• "I am telling the neonatal teams the words acute fetal blood loss so they come with volume, and I want emergency group O RhD-negative red cells brought to theatre."^[8][9]
• "Straight to theatre, general anaesthesia, no delay for tests. I am not sending an Apt or a Kleihauer — the interval from rupture to birth is the only thing that changes the outcome."^[1][5]
• "Her observations being normal does not reassure me at all. The blood is the babies', not hers."^[5]

Probe 5 — "The first twin is pale, floppy and bradycardic after good ventilation. What does it need?"

• "Ventilation and volume. Effective positive-pressure ventilation first, then intravascular access — umbilical venous if possible — then adrenaline and volume expansion if the response is inadequate."^[8]
• "A 10 mL/kg bolus of isotonic saline or red cells over about 5 minutes, repeated according to response."^[9][8]
• "In suspected hypovolaemic arrest, current guidance gives intravenous adrenaline first and then the bolus. A randomised newborn-lamb study of haemorrhagic asphyxial arrest showed that giving the bolus first delayed adrenaline and delayed return of spontaneous circulation."^[9]
• "I would not be reassured by a normal first haemoglobin — haemodilution has not happened yet, so I treat the clinical picture and repeat it."^[8][9]

Probe 6 — communication. "She is crying and says 'Have I done something wrong? Should I have stayed in hospital?'"

Scored domain. Say the words. ^[1][3]

• Sit at her level, use her name: "You have done nothing wrong. This is not something you caused and not something you could have prevented by behaving differently."
• Be honest without blaming: "The reason we watch women with this condition so closely is exactly this — that the membranes can break without warning. That is why we had a plan, and why the team was ready."
• Give her information she can hold: "Both babies are with the neonatal team now. They are giving them fluid and blood to replace what they lost. I will come back and tell you exactly what is happening as soon as I know more."
• Offer support and commit to a debrief: a support person contacted, a named midwife with her, and a formal debrief once the babies are stable.^[1][3]

Probe 7 — "One last thing. Her sister had a scan that said 'low placenta, resolved'. Does she need anything?"

• "Yes. A low placenta that migrates upward can leave a marginal vessel behind over the os — that is type 3 vasa praevia. The consensus recommends transvaginal ultrasound with Doppler at approximately 32 weeks when a low-lying placenta or praevia was found in the second trimester. 'Resolved low placenta' is an indication to look again, not a discharge."^[3][2]