D-dimer (plasma)
D-dimer levels rise progressively during normal pregnancy. A negative result remains useful to help exclude venous thromboembolism in low-risk patients, but positive results are nonspecific and must be interpreted in clinical context.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| µg/mL | < 0.5 | 0.05 – 0.95 | 0.32 – 1.29 | 0.13 – 1.7 |
| µg/L (ng/mL) | < 500 | 50 – 950 | 320 – 1290 | 130 – 1700 |
| nmol/L | < 2.7 | 0.3 – 5.2 | 1.8 – 7.1 | 0.7 – 9.3 |
Physiology in pregnancy
- Pregnancy is a prothrombotic state with increased fibrin turnover and higher D-dimer values.
- D-dimer concentrations typically rise with advancing gestational age, often exceeding the nonpregnant threshold even in uncomplicated pregnancies.
- Trimester-specific reference intervals are preferable to a single nonpregnant cut-off.
Some causes of elevated D-dimer
- Deep vein thrombosis (DVT)
- Pulmonary embolism (PE)
- Disseminated intravascular coagulation (DIC)
- Malignancy
- Underlying inflammation or infection
- Cardiac, renal, or hepatic disease
- Recent surgery or trauma
Clinical notes
- D-dimer testing should be interpreted alongside clinical probability and imaging studies when evaluating suspected venous thromboembolism in pregnancy.
- Different laboratories and assays may report different units or cutoffs; local reference intervals should be consulted.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–1331. PMID: 19935037.
- Kratz A, Ferraro M, Sluss PM, Lewandrowski KB. Laboratory reference values. N Engl J Med. 2004;351(15):1548–1563. PMID: 15470219.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed. Lippincott Williams & Wilkins; 2007.