Risk factors for VTE
History of VTE. The most important risk factor for VTE is a personal history of prior VTE.6 Recurrence risks have been widely reported and depend on the factors surrounding the initial event. For patients with a prior provoked deep vein thrombosis (DVT; associated with trauma or surgery), the antepartum VTE risk likely is less than 1%, and VTE chemoprophylaxis is not recommended antepartum.7
For patients with a prior VTE that was not associated with surgery or trauma (unprovoked), the risk is approximately 3%; for prior VTE related to pregnancy or hormonal contraception, the risk is approximately 6%.7 For both of these groups, prophylactic-dose antepartum is recommended. Patients with recurrent VTE are often taking long-term anticoagulation. Anyone on long-term anticoagulation should be placed on therapeutic-dose antepartum. For patients not receiving long-term anticoagulation, consider a hematology consultation when available, and begin an intermediate-dose or therapeutic-dose regimen after assessing other risk factors and the risk of bleeding and discussing treatment with the patient.
Thrombophilias. The next most important risk factor is the presence of inherited thrombophilias.6 Factor V homozygote, prothrombin G20210A mutation homozygote, antithrombin deficiency, and combined factor V heterozygote and prothrombin G20210A heterozygote (also called compound heterozygote) have the strongest association with VTE in pregnancy.8 It is recommended that patients with these high-risk thrombophilias receive prophylactic-dose antepartum.8
Factor V heterozygote, prothrombin G20210A mutation heterozygote, and protein C or protein S deficiency are considered low-risk thrombophilias. Patients with low-risk thrombophilias and no personal history of VTE or first-degree relative with VTE can be monitored with clinical surveillance antepartum. However, if a family history of VTE or other risk factors for VTE are present, antepartum prophylactic-dose is recommended. Clinical factors to consider antepartum include obesity, age older than 35 years, parity of 3 or higher, varicose veins, immobility, smoking, assisted reproductive technology use, multiple gestation, and preeclampsia.10
Antiphospholipid syndrome (APS) is another high-risk condition. For patients not taking long-term anticoagulation antepartum, prophylactic-dose is recommended. For patients on long-term anticoagulation, therapeutic-dose is recommended.
Other medical conditions. Patients with medical conditions that place them at high risk for VTE may warrant prophylactic-dose antepartum. These include active cancer, active systemic lupus erythematosus, sickle cell disease, nephropathy, and inflammatory bowel disease.10 This decision can be made in conjunction with other specialists caring for the patient.
Antepartum prophylactic-dose is not recommended for low-risk patients as there is less than 1% risk of VTE.7 (TABLE 2 summarizes antepartum chemoprophylaxis recommendations.)
CASE 1 continued Patient develops another VTE risk factor
The patient is being followed with clinical surveillance. At 19 weeks’ gestation, she presents to the emergency department with shortness of breath and fever. She is diagnosed with COVID-19 and is admitted by a medicine service. They call the OB team to ask for recommendations regarding anticoagulation.
What should the next steps include?
Hospitalization and nonobstetric surgery are risk factors for VTE. Many hospitals use a standardized assessment for all inpatients, such as the Padua or Caprini VTE risk assessment scores. These can be modified for use in pregnant patients, although neither scoring system is currently validated for use in pregnancy.5 For any pregnant patient admitted to the hospital, mechanical prophylaxis is recommended.
COVID-19. Infection with the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated clinical syndrome, COVID-19, is associated with increased rates of VTE. Recommendations for pregnant patients with COVID-19 are the same as for the general population. During hospitalization for COVID-19, pregnant patients should be placed on prophylactic-dose chemoprophylaxis. Patients should not be discharged home on chemoprophylaxis, and patients managed as outpatients for their disease do not need chemoprophylaxis.11
Management approach. Prophylactic-dose administration is recommended during hospital stay for all patients admitted with anticipated length of stay of 3 days or longer and who are not at high risk for bleeding or delivery.10 Both LMWH and UFH are options for inpatients. For any nonobstetric surgery or admission, LMWH may be most appropriate. However, as most obstetrics admissions are at increased risk for delivery, UFH 5,000 U twice daily to 3 times daily is the best option to increase the chances for neuraxial anesthesia. (I review anesthesia considerations for delivery later in this article.) For patients at high risk for bleeding or delivery, mechanical prophylaxis alone, with elastic stockings or pneumatic compression devices, can be used.
Continue to: CASE 1 continued Patient is discharged home...