From the Guidelines
D-dimer levels should be interpreted with caution in pregnant women, and markedly elevated D-dimers several-fold above the upper range of normal for pregnancy should be considered as indicative of coagulopathy. The standard cutoff values for D-dimer are less reliable in pregnant women due to the natural increase in D-dimer levels during pregnancy 1. For suspected venous thromboembolism (VTE) in pregnancy, clinicians should use pregnancy-specific D-dimer thresholds or trimester-specific reference ranges when interpreting results.
Some key points to consider when interpreting D-dimer levels in pregnant women include:
- D-dimer levels may be 1.5-2 times higher than non-pregnant values in the first trimester, and 3-4 times higher in the second and third trimesters 1
- A negative D-dimer result using appropriate pregnancy-adjusted thresholds still has value in ruling out VTE, but a positive D-dimer test requires further diagnostic imaging such as compression ultrasonography for suspected deep vein thrombosis or CT pulmonary angiography for suspected pulmonary embolism 1
- Clinical assessment using validated tools like the modified Wells score remains important when evaluating pregnant patients with suspected VTE, even with adjusted D-dimer interpretation 1
It is essential to note that the use of D-dimer in pregnancy is still a topic of debate, and the decision to use it should be made on a case-by-case basis, taking into account the individual patient's risk factors and clinical presentation. The most recent and highest quality study suggests that D-dimer levels should be interpreted with caution, and markedly elevated levels should be considered as indicative of coagulopathy 1.
From the Research
D-Dimer Levels in Pregnancy
- D-dimer levels increase progressively throughout pregnancy, with significant increases in the second and third trimesters 2, 3, 4, 5, 6
- The increase in D-dimer levels is associated with increased thrombin activity and fibrinolysis following fibrin formation 2
- Reference values for D-dimer according to gestational age need to be established for accurate diagnosis and prediction of venous thromboembolic events (VTE) or pregnancy-related complications 2, 3, 4
Trimester-Specific Reference Intervals
- Trimester-specific reference intervals for D-dimer have been established in some studies:
- These reference intervals may vary depending on the assay used and the population studied 4
Clinical Implications
- The D-dimer test has limited use in ruling out VTE in the third trimester if a cutoff of 0.50 mg/L is used 3
- A large management study is needed to establish new thresholds for the D-dimer to rule out VTE in each trimester 3
- Women with D-dimer levels higher than 3.2 µg/mL may be at increased risk of pulmonary thromboembolism and should be closely monitored 5