VTE Risk Assessment and Management in Pregnant Women
The Royal College of Obstetricians and Gynecologists (RCOG) risk scoring system is the most validated approach for assessing VTE risk in pregnant women, with management guided by specific score thresholds that determine the need for prophylactic anticoagulation. 1
Risk Scoring System for Pregnant Women
RCOG Weighted Risk Assessment Model
The RCOG risk assessment model assigns weighted scores to various risk factors:
Pre-existing Risk Factors:
- Previous VTE (except a single event related to major surgery): 4 points
- Previous unprovoked/estrogen-related VTE: 3 points
- Known high-risk thrombophilia: 3 points
- Medical comorbidities (heart/lung disease, SLE, cancer, inflammatory conditions): 3 points
- Family history of unprovoked/estrogen-related VTE in first-degree relative: 1 point
- Known low-risk thrombophilia: 1 point
- Age >35 years: 1 point
- BMI >30 kg/m²: 1 point
- Parity ≥3: 1 point
- Smoker: 1 point
- Gross varicose veins: 1 point
Obstetric Risk Factors:
- Pre-eclampsia: 1 point
- Cesarean section in labor: 2 points
- Elective cesarean section: 1 point
- Mid-cavity/rotational forceps delivery: 1 point
- Prolonged labor (>24 hours): 1 point
- Postpartum hemorrhage (>1L or transfusion): 1 point
- Preterm birth <37 weeks: 1 point
- Stillbirth: 1 point
Transient Risk Factors:
- Surgical procedure during pregnancy or puerperium: 3 points
- Hyperemesis: 3 points
- Ovarian hyperstimulation syndrome: 4 points
- Current systemic infection: 1 point
- Immobility/dehydration: 1 point
Management Based on Risk Score
Antepartum Management:
- Score ≥4: Consider thromboprophylaxis with LMWH throughout pregnancy
- Score 3: Consider thromboprophylaxis with LMWH from 28 weeks
- Score <3: Clinical surveillance (no pharmacological prophylaxis)
Postpartum Management:
- Score ≥2: Thromboprophylaxis with LMWH for at least 10 days
- Score ≥3 with additional risk factors: Extended thromboprophylaxis for 6 weeks
- Score <2: Clinical surveillance
Special Considerations for Thrombophilia
Factor V Leiden or Prothrombin Gene Mutation (Heterozygous):
- Antepartum: Clinical surveillance recommended unless additional risk factors present
- Postpartum:
- Without family history of VTE: Clinical surveillance
- With family history of VTE: Prophylaxis for 6 weeks
Protein C Deficiency:
- Antepartum: Clinical surveillance recommended unless additional risk factors present
- Postpartum: Consider prophylaxis if combined with other risk factors
Evidence Quality and Limitations
The evidence supporting these recommendations is of low to moderate quality. The prediction model for postpartum VTE risk developed using UK data showed good performance characteristics (C statistic: 0.73; 95% CI, 0.71-0.75) 1, but prospective validation is limited.
Studies evaluating risk scoring systems have shown low VTE rates when prophylaxis is guided by these scores, but the absence of comparator arms makes it difficult to assess the true impact 1. A controlled before-and-after implementation study showed that risk score-driven prophylaxis reduced VTE incidence (RR = 0.30 [0.14; 0.67]) without significantly increasing bleeding risk 2.
Common Pitfalls and Caveats
Inconsistent application: Different institutions may use different cutoff points for risk categories, leading to variable management decisions 3. Standardized application of the RCOG scoring system is essential.
Overestimation of risk: Some scoring systems (like Caprini) may classify up to 94% of pregnant women as high risk, resulting in unnecessary anticoagulation 4.
Underestimation of risk: The Padua risk assessment model may miss VTE cases in pregnant women 4.
Timing of prophylaxis: Failure to recognize that VTE risk increases from conception and extends through the postpartum period 1.
Monitoring requirements: When using LMWH, monitoring anti-Factor Xa levels may be necessary, with target ranges of 0.2-0.6 U/mL for prophylactic dosing 5.
The RCOG scoring system represents the most practical approach to balancing the risks of VTE against the potential harms of unnecessary anticoagulation in pregnant women. Implementation of this standardized approach has been shown to improve consistency of care and reduce VTE events without increasing hemorrhagic complications 6.