The risk of venous thromboembolism (VTE) in pregnancy is approximately five times higher than in non-pregnant women of the same age and remains the leading cause of maternal mortality in first world nations1-4.
|Risk of VTE in pregnancy increases further in those with maternal related medical conditions such as pre-eclampsia and HELLP, multi-parity, caesarean section, large-post-partum haemorrhage, personal or family history of thromboembolism, inherited thrombophilias, anti-phospholipid syndrome, patients with a high BMI, maternal age >35, renal disease, immobilisation and in women who smoke5. Despite this well recognised increased risk and the mortality and morbidity that is associated with VTE in pregnancy, there remains a scarcity of evidence with no standardised guidelines to assist clinicians in diagnostic workup and treatment options.|
Risk of VTE in pregnancy increases further in those with maternal related medical conditions such as pre-eclampsia and HELLP, multi-parity, caesarean section, large-post-partum haemorrhage, personal or family history of thromboembolism, inherited thrombophilias, anti-phospholipid syndrome, patients with a high BMI, maternal age >35, renal disease, immobilisation and in women who smoke5. Despite this well recognised increased risk and the mortality and morbidity that is associated with VTE in pregnancy, there remains a scarcity of evidence with no standardised guidelines to assist clinicians in diagnostic workup and treatment options.
How common is pregnancy related thromboembolism?
Thankfully the incidence of deep vein thrombosis and pulmonary embolism remains rare in pregnancy, with a reported incidence of around 1-2 per 1000 deliveries1-2. Approximately 80% of these are deep vein thrombosis with the remaining 20% presenting as pulmonary embolus, with arterial thrombotic events being exceptionally uncommon. Many of these thrombotic events occur at the time of delivery or within six weeks post-partum5-6.
Working up a patient with pregnancy related thromboembolism
Ultrasound scan of the lower limbs remains the most useful and readily available tool in working up a patient with a suspected deep vein thrombosis who have a sensitivity of 97% and specificity of 94%6. However, a gravid uterus and pelvic or proximal embolisms can be difficult to assess with USS. MRI scans should be considered in this instance if readily accessible with a sensitivity of 98.5%7. A ventilation-perfusion (VQ) scan is my preference over a CTPA due to the lower radiation burden in patients where there remains a high level of suspicion for a pulmonary embolus with a negative US scan or MRI8. Using risk stratifications scores such as Wells or biochemical measurements such as D-dimer are not useful in pregnancy.
Recommended treatment options
Low molecular weight heparin (LMWH) remains the treatment of choice for VTE in the antepartum or post-partum period. While no evidence exists for once daily dosing vs twice daily dosing, my practice leans towards twice daily dosing due to the increased renal clearance in pregnancy. However, this needs to be personalised to the patient, their likelihood of compliance and other co-morbidities. Initial dosing is based on the patient’s actual body weight. I recommend monitoring the Anti-Xa level every six to eight weeks to ensure the patient remains within therapeutic levels.
As warfarin crosses the placenta and is highly teratogenic, use of warfarin should be avoided especially during organogenesis in the first trimester of pregnancy4-6. Direct thrombin inhibitors and anti-Xa inhibitors should also be avoided in pregnancy due to the animal toxicity reported by manufacturers.
Patient management during delivery
Management of delivery needs to be done in close correlation with the obstetrician and the patient, particularly regarding their labour preferences (i.e. use of spinal anaesthesia or planned caesarean section). Switching from LMWH to an unfractionated heparin (UFH) infusion is preferable in the days leading up to a planned induction or caesarean, followed by stopping the infusion as soon as active labour starts or four hours prior to planned surgical intervention4,6. Re-initiation of anticoagulation should be started 24-48 hours after an uncomplicated delivery.
Dr Renee Squires is a clinical haematologist consulting at Icon Cancer Centre in Southport and South Brisbane, and Bryants Road Medical Centre in Logan. Dr Squires also participates in Icon’s BloodLine (0458 667 866) which provides GP’s with 24-hour access to advice on clinical haematological cases, expedited referrals and specialist consultations. For more information, visit iconcancercentre.com.au/doctor/renee-squires/
This article was written by Dr Renee Squires.
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