VTE in Pregnancy

• Pregnancy increases the risk of VTE (highest risk in 3rd trimester and in the first 6 weeks postpartum)
• DVT
  • 80% in the left leg (due to left iliac compression)
  • 60% in the iliofemoral vein. Tends to present with back/buttock/thigh pain as opposed to calf pain.
• PE
  • difficult to clinically diagnose as dyspnea and tachycardia can be normal in pregnancy

Diagnosis of VTE

ARTEMIS / Pregnancy-Adapted YEARS Algorithm

This was a study published in NEJM by van der Pol et al. in 2019 that examined a strategy using pregnancy-adapted YEARS in the diagnosis of PE in pregnant women.

Population: Adult women with chest pain or dyspnea presenting to hospital. Intervention: YEARS criteria (s/s of DVT, hemoptysis, and PE as the most likely Dx), combined with the D-dimer (<500 or <1000).

• Low pretest probability: 0/3 YEARS, D-dimer <1000; effectively excluded PE
• Higher pretest probability: 1+ YEARS, D-dimer <500

Conclusion: in a low PTP setting (low D-dimer and 0 YEARS), CTPE is not required to rule out PE in pregnant women.

This study is polarizing and a single study; not guideline based yet. Therefore for the RCE, do not follow this study.

Imaging Modalities

• Doppler leg ultrasound
  • 91% sensitivity, NPV 99%
  • however, cannot rule out DVT with a single ultrasound
  • need to ensure visualisation of the proximal veins (iliac, femoral) to the popliteal veins
• V/Q vs CTPA
  • V/Q scan is first-line according to SOGC/Thrombosis Canada/ACCP
  • V/Q has less radiation for the mother than CTPA (risk of breast cancer), but slightly greater risk of radiation to the fetus (childhood cancer)
• No imaging?
  • For now, D-dimer and clinical pretest probability (Well's/YEARS) is NOT recommended for diagnosis if pregnancy. Pregnant women SHOULD undergo diagnostic imaging.

Radiation Counselling

• 1 rad = 10 mGy = 10 mSv
• 10 rads is the required dose for teratogenicity or miscarriage
• The acceptable upper limit in pregnancy is <5 rad
• Maternal radiation
  • CTPA <0.5 rad
  • VQ 0.007-0.03 rad
  • CXR 0.005 rad

Management of Acute VTE in Pregnancy

Duration: minimum 3 months including 6 weeks post-partum Drug: LMWH or UFH Considerations:

• weight based dosing
• once or twice daily dosing
• Xa level monitoring? (not routinely recommended)
• risk of bleeding and HIT

Other Treatments

• Warfarin is contraindicated in pregnancy
  • first trimester: warfarin embropathy (mid-facial and limb hypoplasia and stippledbone)
  • second-third trimesters: neurologic abnl, microcephaly, optic atropy, neonatal haemorrhage
• DOACs are not recommended in pregnant or breastfeeding women
• tPA only for life threatening and hemodynamically unstable
• HIT: fondaparinux, consult hematology
• IVC filter: same indications as outside of pregnancy. Consider use if the VTe is newly diagnosed close to delivery (<2-4 weeks). Needs prompt removal post-partum and hematology consultation.

Management of VTE Peri-Partum

• If the woman is on therapeutic AC:
  • Planned delivery
    • withhold LMWH for 24 hours pre-neuraxial analgesia
    • Admit for UFH if VTE diagnosed <4 weeks of delivery, and hold 6 hours pre-neuraxial analgesia
  • Spontaneous labour --> withhold anticoagulation
• If the woman is on prophylactic AC:
  • Withhold LMWH anticoagulation 12 hours pre-neuraxial analgesia
• Post-partum
  • restart AC 4 hours post removal of neuraxial anesthesia
  • generally this is 4-6 hours post vaginal delivery, 6-8 hours post CS if hemostasis is achieved

Anticoagulants and Breast-Feeding

Safe in breastfeeding: LMWH, UFH, fondaparinux/danaparoid, warfarin. Not safe in breastfeeding: DOAC

While on anticoagulation, women need to be on contraception (avoid estrogen based contraceptives). This essentially means that they need to consider progestin only pill, Progestin based IUD, or surgical contraception.

VTE prophylaxis in pregnancy