SUMMARY:  

The CMQCC Maternal VTE Task Force protocols are modeled on risk stratification.  VTE risk is separated in to three levels (Low, Medium, High), with thromboprophylaxis targeted to each level.  The Task Force also identified key moments in pregnancy that require specific risk assessment, including delivery.  

For women undergoing cesarean birth, CMQCC recommends  

• Pharmacologic prophylaxis for women undergoing cesarean section with BMI ≥ 35 kg/m2 
• Other women with a single major or two or more minor risk factors should also receive in-house post cesarean pharmacologic prophylaxis 

VTE and Cesarean Section  

Major VTE Risk Factors for Use With Algorithm Below 

• BMI >35 kg/m2 @ delivery 
• Low-risk thrombophilia 
• Postpartum hemorrhage requiring 
  • Transfusion  
  • Further operation (e.g., hysterectomy, D&C)  
  • Interventional Radiology procedure 
• Infection requiring antibiotics 
• Antepartum hospitalization ≥ 72 hours, current or within the last month 
• Chronic medical conditions 
  • Sickle Cell disease 
  • Systemic Lupus Erythematosus 
  • Significant Cardiac disease 
  • Active Inflammatory Bowel Disease 
  • Active cancer 
  • Nephrotic syndrome 

Minor VTE Risk Factors 

• Multiple gestation 
• Age >40 years 
• Postpartum hemorrhage ≥1000 ml but not requiring  
  • Transfusion  
  • Further operation (e.g., hysterectomy, D&C)  
  • Interventional Radiology procedure 
• Family history of VTE  
  • VTE occurring in a first-degree relative prior to age 50 
• Smoker 
• Preeclampsia 

Cesarean Section Risk Assessment  

LOW RISK 

• Not meeting medium or high risk criteria 

MECHANICAL PROPHYLAXIS

MEDIUM RISK

• Cesarean Delivery with 1 Major or >2 Minor Risk Factors (see above)

MECHANICAL PROPHYLAXIS and PROPHYLACTIC DOSE LMWH/UFH (postpartum, until discharge)

HIGH RISK  

• High-risk thrombophilia (including acquired such as APS) with no prior history of VTE and regardless of family history
• Prior provoked, idiopathic, or estrogen related VTE
• Low risk thrombophilia AND family history of VTE OR single prior VTE
• Patients already receiving LMWH/UFH as outpatient
• Multiple prior VTE
• Prior VTE with High Risk thrombophilia (including APS)

(1) MECHANICAL PROPHYLAXIS and PROPHYLATIC DOSE LMWH/UFH (postpartum, until 6 weeks from date of delivery or 

(2) MECHANICAL PROPHYLAXIS and THERAPEUTIC DOSE LMWH/UFH (postpartum dose ≥ antepartum dose) in hospital and continued until 6 weeks from delivery date after discharge

Vaginal Birth Risk Assessment  

LOW RISK 

• Delivery BMI >40 kg/m2

MECHANICAL PROPHYLAXIS   

MEDIUM RISK 

• Delivery BMI > 40 kg/m2 and Antepartum hospitalization ≥ 72 hours is anticipated currently or within past month 
• Delivery BMI > 40 kg/m2 and Low Risk Thrombophilia 

MECHANICAL PROPHYLAXIS and PROPHYLACTIC DOSE LMWH / UFH (postpartum hospitalization)

Note: Consider LMWH/UFH continuation for 6 weeks postpartum if BMI≥40 kg/m2 and thrombophilia

HIGH RISK 

• High-risk thrombophilia with no prior history of VTE regardless of family history 
• Prior provoked, idiopathic, or estrogen related VTE 
• Low risk thrombophilia AND family history of VTE 
• ANY single prior VTE 
• Patients already receiving LMWH/UFH as outpatient 
  • Multiple prior VTE 
  • Prior VTE with high risk thrombophilia or APS 

(1) MECHANICAL PROPHYLAXIS and PROPHYLACTIC DOSE LMWH/UFH (postpartum in hospital until 6 weeks from date of delivery after discharge) or 

(2) MECHANICAL PROPHYLAXIS and THERAPEUTIC DOSE LMWH / UFH (Postpartum in hospital and continued until 6 weeks from date of delivery after discharge, with postpartum dose ≥antepartum dose)

Notes:  

• Mechanical prophylaxis should be placed prior to cesarean and continued until ambulatory 
• The CMQCC Maternal VTE Task Force supports the ACOG recommendations that women with prior VTE events, high-risk thrombophilia, or low risk thrombophilia with family history of VTE receive postpartum pharmacologic prophylaxis  
  • Internal California data corroborate the finding of increased risk for maternal VTE mortality with increasing BMI and immobility >72 hours during hospitalization  
  • Therefore, CMQCC has included BMI ≥40 kg/m2 in combination with current, anticipated or recent (within the past month) hospitalization for ≥72 hours for intrapartum mechanical prophylaxis and/or postpartum pharmacologic prophylaxis 

KEY POINTS:  

• At all risk levels, all women undergoing cesarean section should  
  • Be encouraged to ambulate 
  • Avoid dehydration  
  • Receive mechanical prophylaxis 

Definitions – Risk Factors  

FAMILY HISTORY of VTE 

• VTE occurring in a first-degree relative prior to age 50 

HIGH RISK THROMBOPHILIA   

• Antithrombin III deficiency 
• Antiphospholipid syndrome (APS)  
  • Requires at least one clinical and one laboratory criteria be met  
• Factor V Leiden or Prothrombin pathogenic variant  
  • Homozygosity or compound heterozygosity 

LOW RISK THROMBOPHILIA

• Factor V Leiden or Prothrombin pathogenic variant  
  • Heterozygote state  
• Protein C or S deficiency 

Definitions – Anticoagulation Regimens (ACOG)

LMWH – PROPHYLACTIC

• Enoxaparin, 40 mg SC once daily
• Dalteparin, 5,000 units SC once daily
• Tinzaparin, 4,500 units SC once daily
• Nadroparin, 2,850 units SC once daily

LMWH – INTERMEDIATE DOSE

• Enoxaparin, 40 mg SC every 12 hours
• Dalteparin, 5,000 units SC every 12 hours

LMWH – ADJUSTED DOSE (THERAPEUTIC)  

• Enoxaparin, 1mg/kg SC every 12 hours
• Dalteparin, 200 units/kg SC once daily
• Tinzaparin, 175 units/kg SC once daily
• Dalteparin, 100 units/kg SC every 12 hours

UFH – PROPHYLACTIC   

• UFH, 5,000 to 7,500 units SC every 12 hours in first trimester
• UFH, 7,500 to 10,000 units SC every 12 hours in the second trimester
• UFH, 10,000 units SC every 12 hours in the third trimester, unless the aPTT is elevated

UFH – ADJUSTED DOSE (THERAPEUTIC)

• UFH, 10,000 units or more SC every 12 hours in doses adjusted to target aPTT in the therapeutic range (1.5 to 2.5 X control) 6 hours after the injection

POSTPARTUM ANTICOAGULATION  

• Prophylactic, intermediate or adjusted dose LMWH for 6 to 8 weeks as indicated
• Oral anticoagulants may be considered postpartum based upon planned duration of therapy, lactation and patient preference

SURVEILLANCE    

• Clinical vigilance and appropriate objective investigation of women with symptoms suspicious of deep vein thrombosis or pulmonary embolism
• VTE risk assessment should be performed prepregnancy or early in pregnancy and repeated if complications develop, particularly those necessitating hospitalization or prolonged immobility

Notes:  

• Anti-Xa level testing is available to monitor activity of LMWH agents 
• CMQCC defines ‘LMWH therapeutic dose’ as enoxaparin, 1mg/kg SC every 12 hours, adjusted to target Xa 0.6-1.0 units/mL 4-6 hours after injection with acute VTE
• aPTT testing is used to determine UFH dosing, not LMWH activity 
• Anti-Xa level testing is not currently mandated due to cost, inconvenience and lack of high quality data 
• Dose adjustment may be considered with extremes of body weight (<50 kg or >90 kg)
• Consultation and ongoing collaboration with Anesthesia is strongly recommended 

CMQCC Maternal VTE Patient Education Handout

Learn More – Primary Sources:

CMQCC Venous Thromboembolism Toolkit

ACOG Practice Bulletin 196: Thromboembolism in Pregnancy

ACOG District II/Safe Motherhood Initiative: Maternal Safety Bundle for Venous Thromboembolism

International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS)

Locate a genetic counselor or genetics services:

Genetic Services Locator-ACMG

Genetic Services Locator-NSGC

Genetic Services Locator-CAGC

Locate a Maternal Fetal Medicine Specialist

Maternal Fetal Medicine Specialist Locator-SMFM

Related ObG Topics:

The CMQCC Toolkit: Venous Thromboembolism and Antepartum Admission (Non-Delivery)

The CMQCC Toolkit: Pregnancy Related Risk Factors & Thrombophilia Defined

Venous Thromboembolism Prophylaxis in Early Pregnancy