Mechanical valve in pregnancy — structured SAQ (15 marks)

(a) Modified WHO risk class and reasoning (3 marks)

One mark for the class, one for the reasoning, one for the management implication. ^[1]

• Modified WHO class III. A mechanical valve in pregnancy is significantly increased risk of maternal mortality or severe morbidity, requiring expert counselling and cardio-obstetric care throughout.^[1]
• Reasoning: the mechanical valve carries a high maternal thrombosis risk in the hypercoagulable state of pregnancy, and anticoagulation is mandatory but each option creates a trade-off between maternal thrombosis and fetal harm. The ROPAC registry data confirm this risk profile.^[2]
• Management implication: she needs care at a centre with a cardio-obstetric team, planned delivery at a tertiary centre, and high-dependency or intensive care monitoring postpartum. The postpartum haemodynamic surge is the highest-risk window.^[1]

(b) The three anticoagulation strategies and their trade-offs (5 marks)

One mark for each strategy named, one mark for each trade-off stated, and one mark for the explicit shared decision-making statement. ^[1][2]

• Strategy 1 — warfarin throughout with switch close to delivery. Continue warfarin until 36 weeks, then switch to low-molecular-weight heparin, and then intravenous unfractionated heparin close to delivery. Lowest maternal thrombosis risk; highest fetal embryopathy risk (warfarin in weeks 6 to 12 causes fetal warfarin syndrome, fetal loss, and intracranial haemorrhage).^[1]
• Strategy 2 — low-molecular-weight heparin throughout with anti-Xa monitoring. Twice-daily low-molecular-weight heparin with peak anti-Xa 0.8 to 1.2 units per millilitre, dose-adjusted to maintain therapeutic range. Lowest fetal risk (LMWH does not cross the placenta); higher maternal thrombosis risk when anti-Xa targets are not met, especially if doses are missed.^[1][2]
• Strategy 3 — hybrid: low-molecular-weight heparin in weeks 6 to 12, then warfarin. Use LMWH during the embryopathy window, then switch to warfarin for the second and third trimester. Balances both risks; intermediate overall.^[1]
• The trade-off must be stated explicitly: warfarin throughout has the lowest maternal valve thrombosis rate but the highest fetal loss and embryopathy rate; LMWH throughout has the lowest fetal risk but a higher maternal thrombosis rate when anti-Xa targets are not met. The ROPAC registry (van Hagen 2015) and the recent update (van der Zande 2026) confirm these trade-offs.^[2][3]
• Shared decision-making: present all three strategies with their trade-offs, document the woman's informed choice, and provide written information. The 2018 ESC Guidelines recommend this approach.^[1]

(c) Peripartum management plan (5 marks)

One mark each for the mode of delivery, the timing, the anaesthetic plan, the anticoagulation transition, and the postpartum surveillance. ^[1][6]

• Mode of delivery: vaginal delivery is preferred unless there is an obstetric indication for caesarean. A short second stage with assisted delivery (forceps or ventouse) reduces the cardiac output spike of pushing and the risk of valve-related complications.^[1]
• Timing: planned delivery around 39 weeks for an uncomplicated mechanical valve, individualised if complications arise. Induction of labour is the typical approach.^[1]
• Anaesthetic plan: early neuraxial analgesia with a slow epidural top-up or low-dose combined spinal-epidural is preferred for labour. Coordinate the timing with the last anticoagulant dose — neuraxial insertion requires a defined interval after the last LMWH dose (usually 24 hours) or after stopping the unfractionated heparin infusion (usually 4 to 6 hours) to minimise the risk of epidural haematoma. General anaesthesia for caesarean if neuraxial is contraindicated.^[1][5]
• Anticoagulation transition: if she is on warfarin until 36 weeks, switch to LMWH at 36 weeks, then intravenous unfractionated heparin at the onset of labour or 4 to 6 hours before a planned caesarean. Stop the unfractionated heparin infusion 4 to 6 hours before the anticipated time of neuraxial insertion. Restart unfractionated heparin 4 to 6 hours after delivery, then transition back to LMWH, then warfarin from day 2 to 5 postpartum.^[1]
• Postpartum surveillance: high-dependency or intensive care monitoring for 24 to 48 hours postpartum, because the postpartum haemodynamic surge is the highest-risk window for cardiac decompensation. Bridge from heparin back to warfarin postpartum, with continued warfarin for at least 6 weeks postpartum given the high thrombosis risk of the puerperium.^[1]

(d) Contraception and long-term follow-up (2 marks)

One mark each for contraception and follow-up. ^[1]

• Contraception counselling: offer reliable contraception before discharge. The progesterone-only options (progesterone-only pill, depo medroxyprogesterone, etonogestrel implant, levonorgestrel intrauterine system) are usually preferred for cardiac disease. Combined oestrogen-progestogen methods are contraindicated in mechanical valves because of the increased thrombosis risk.^[1]
• Long-term follow-up: structured cardiology follow-up including preconception counselling for the next pregnancy. Review of the valve function at intervals, and consider the option of valve replacement to a tissue valve (which does not require anticoagulation but has a shorter lifespan) if she is planning more pregnancies.^[1][4]