Venous thromboembolism in pregnancy — structured oral station (12 minutes)

Opening prompt — "What is your working diagnosis and your immediate actions?"

Model response, in this order: ^[1][2]

• "This is suspected pulmonary embolism complicating a hypercoagulable late pregnancy in a high-risk woman. The risk factors (BMI 38, prior operative delivery, family history, late pregnancy) and the clinical presentation (sudden dyspnoea, pleuritic chest pain, haemoptysis, tachycardia, hypoxaemia, loud P2) all support the diagnosis."
• "I would call for help: consultant obstetrician, anaesthetist, and the medical team. Initiate high-flow oxygen to maintain saturations above 95 per cent, intravenous access, bloods including coagulation, troponin and group and save, ECG, and left lateral tilt to relieve aortocaval compression."
• "I would initiate therapeutic low-molecular-weight heparin immediately, before imaging. The patient is haemodynamically stable but is at high risk of decompensation, and a delay in anticoagulation is unsafe in a patient with high pretest probability."^[1]

Examiner is listening for: the recognition of PE, the multidisciplinary call, the immediate therapeutic LMWH, and the d-dimer correctly interpreted as not diagnostic. ^[5]

Probe 1 — "What is your imaging choice and why?"

• "Ventilation-perfusion scanning is the preferred first-line modality because the chest X-ray is normal. The advantage over CT pulmonary angiography is the lower maternal breast radiation dose, which reduces the lifetime risk of radiation-induced breast cancer."^[2][3]
• "The fetal radiation dose from V/Q scanning is slightly higher than from CTPA but both are well below the threshold of harm. I would arrange the V/Q scan urgently."^[2]
• "If the chest X-ray had been abnormal, I would have used CT pulmonary angiography instead."^[2]

Probe 2 — "What therapeutic dose of LMWH would you give?"

• "Enoxaparin 1 milligram per kilogram subcutaneously twice daily, or 1.5 milligrams per kilogram once daily. For this 90-kilogram woman, the twice-daily dose is 90 milligrams subcutaneously twice daily."^[1][8]
• "I would monitor anti-Xa levels in late pregnancy, with a target peak anti-Xa 0.5 to 1.0 units per millilitre for twice-daily dosing, taken 4 hours after the dose."^[1]
• "Alternatives: dalteparin 200 IU per kilogram once daily, or tinzaparin 175 IU per kilogram once daily."^[1]

Probe 3 — "The V/Q scan confirms multiple segmental perfusion defects. How long will she need treatment?"

• "For acute VTE in pregnancy, 3 to 6 months or at least 6 weeks postpartum, whichever is longer. In this case, the woman is at 34 weeks gestation, so treatment continues until at least 6 weeks postpartum."^[1]
• "She would also require antenatal prophylactic LMWH in any future pregnancy, given the index event. The recurrence risk is in the order of 5 to 15 per cent in subsequent pregnancies depending on prior provoked versus unprovoked status and thrombophilia."^[1][7]

Probe 4 — "Outline the peripartum plan."

• "Plan induction of labour at 39 weeks. Stop enoxaparin 24 hours before the planned induction. Switch to intravenous unfractionated heparin, which can be stopped 4 to 6 hours before anticipated delivery and 4 to 6 hours before neuraxial insertion."^[1]
• "Restart unfractionated heparin 4 to 6 hours after delivery if there is no bleeding, then transition back to LMWH for 6 weeks postpartum. Consider transition to warfarin from day 2 to 5 postpartum if she prefers, with the standard overlap of 5 days until the INR is in the target range."^[1]
• "Anaesthetic plan: early neuraxial analgesia with a slow epidural top-up, provided the anticoagulation has been correctly transitioned. General anaesthesia for caesarean if neuraxial is contraindicated."^[1][6]

Probe 5 — "Should you thrombophilia test this woman?"

• "Thrombophilia testing is selective, guided by the personal and family history. In this case the woman has a first-degree relative with a PE, and testing is reasonable to guide the duration of anticoagulation and the prophylaxis plan for future pregnancies."^[1]
• "Testing is best done at least 6 weeks after the acute event and not during pregnancy or while on anticoagulation, because acute phase changes and heparin affect some assays. I would arrange testing at the postpartum review."^[1]
• "The implications for the woman and her first-degree relatives should be discussed before testing, including the implications of finding an inherited thrombophilia for family screening and counselling."^[1]

Probe 6 — "Tell her what is happening, in language she will understand."

This is scored. Demonstrate it out loud rather than describing it. ^[1]

• Sit down, at her eye level, with her partner or support person present if she wishes.
• Plain words: "We think you may have a blood clot on your lung — a pulmonary embolism. The reason we think this is the way you have suddenly become short of breath and the chest pain you are having, with your risk factors in late pregnancy."
• Stop and acknowledge: "This is a serious condition and I have called the team to look after you. We are starting a blood-thinning injection now to stop the clot growing."
• The plan: "We are going to do a scan — a ventilation-perfusion scan — to confirm the diagnosis. The scan involves breathing in a small amount of a safe gas and having a small injection, and it shows us how the blood is flowing through your lungs. We will keep you on the blood-thinner for the rest of the pregnancy and for 6 weeks after the birth."
• Outcome honesty: "Most women do well with this treatment, but I want to be honest with you about what is happening as we go. We will plan the birth carefully so that the blood-thinner is changed at the right time to keep you safe."
• Offer to call her support person, allocate a named midwife, and commit to a follow-up conversation.^[1]

Probe 7 — "What contraception would you recommend postpartum?"

• "Progesterone-only options are preferred — the progesterone-only pill, depo medroxyprogesterone, the etonogestrel implant, or the levonorgestrel intrauterine system. Combined oral contraception is contraindicated in this woman because of the elevated VTE risk."^[1]
• "I would counsel her before discharge and arrange the chosen method. The levonorgestrel intrauterine system has the additional benefit of treating heavy menstrual bleeding, which is relevant to a woman on long-term anticoagulation."^[1]

Probe 8 — "What would change if she were to develop a massive PE with cardiac arrest?"

• "This is the multidisciplinary emergency. I would call the team immediately — consultant obstetrician, anaesthetist, intensivist, haematology, interventional radiology — and follow the obstetric cardiac arrest pathway."^[1]
• "Treatment is intravenous alteplase for massive PE with haemodynamic compromise, with the option of catheter-directed thrombolysis or surgical embolectomy in selected cases."^[1]
• "Perimortem caesarean for maternal salvage is performed within 4 to 5 minutes of cardiac arrest onset, at the level of the bed, with the team continuing resuscitation. It improves maternal survival independent of gestational age."^[1]