How long postpartum is the D-dimer (D-dimer) test expected to remain positive?

From the Guidelines

D-dimer levels are expected to remain elevated for approximately 4-6 weeks postpartum due to the physiological changes that occur after delivery. After delivery, the body undergoes significant hemostatic changes as it returns to a non-pregnant state, including the gradual clearance of fibrin degradation products 1. The elevation occurs because pregnancy and delivery create a hypercoagulable state with increased fibrin formation and breakdown. D-dimer levels peak during delivery and the immediate postpartum period, then gradually decline. This normal physiological elevation can complicate the diagnosis of venous thromboembolism in postpartum women, as D-dimer is commonly used to rule out this condition. Healthcare providers should interpret D-dimer results cautiously during this period and may rely more heavily on clinical assessment and imaging studies when evaluating postpartum women for possible thrombotic events, as suggested by guidelines for the management of cardiovascular diseases during pregnancy 1. Some key points to consider when evaluating postpartum women for thrombotic events include:

• The use of D-dimer measurement and compression ultrasonography in patients with suspected VTE during pregnancy 1
• The recommendation for antenatal prophylaxis with LMWH in high-risk patients, as well as post-partum prophylaxis for the duration of 6 weeks 1
• The importance of clinical judgment and a high index of suspicion when evaluating postpartum women for possible thrombotic events, due to the limitations of D-dimer testing in this population 1. The exact duration of elevation can vary between individuals, with some women returning to normal levels earlier and others experiencing prolonged elevation.

From the Research

D-dimer Levels Postpartum

• D-dimer levels are expected to be elevated after delivery and may remain so for several weeks 2, 3.
• Studies have shown that D-dimer levels decrease quickly during the first 3 days post-delivery, but may take many weeks to normalize 2.
• One study found that at day 30 and day 45 postpartum, 79% and 93% of women in the vaginal delivery group and 70% and 83% in the cesarean group had D-dimer levels below 500 ng mL(-1) 3.
• The utility of D-dimer measurement to rule out venous thromboembolism (VTE) is limited until 4 weeks postpartum 2, 3.
• Using a cut-off at 500 ng mL(-1), D-dimer measurement for ruling out VTE was found to be useful again 4 weeks after delivery 3.

Factors Affecting D-dimer Levels

• Bleeding, breastfeeding, and heparin prophylaxis did not modify D-dimer levels significantly 3.
• The increase in D-dimer values until 4 to 6 weeks after delivery correlates with the length of antithrombotic prophylaxis recommended for women at high risk of VTE 2.

Reference Intervals for D-dimer

• Reference intervals for D-dimer during the postpartum period have been established, with a cut-off at 500 ng mL(-1) 3.
• Trimester-specific reference intervals for D-dimer during pregnancy have also been established, with D-dimer levels increasing progressively and significantly through pregnancy 4.