In plain words
D-dimer is a blood test. It measures a small piece of protein that appears when a blood clot breaks down. A normal result means a clot is unlikely in most settings. In pregnancy the level rises naturally, so a high result does not mean a clot is present. Clinicians know this and use the test with care. When a mother has leg swelling, chest pain, or shortness of breath, a provider may order a D-dimer and then a scan. A high value leads to imaging, not to a diagnosis on its own. Mothers are not usually told a D-dimer number. The question for a mother is what symptoms she has and whether she should be seen now.
The deeper version
D-dimer is a cross-linked fibrin degradation product. Its concentration rises physiologically across pregnancy and in the early postpartum period, which lowers the specificity of the assay. Pregnancy-adjusted cut-offs have been proposed, and the Royal College of Obstetricians and Gynaecologists Green-top Guideline 37a on thromboprophylaxis (2015) and ACOG Practice Bulletin 196 on thromboembolism in pregnancy (2018) note the limited diagnostic value of the test in pregnancy. Its high negative predictive value makes a normal result useful in low-risk settings, while a positive result usually requires or CT pulmonary angiography. Controversy remains about whether pregnancy-specific thresholds improve accuracy enough to change practice.
Where it comes up
- Blood clots: the signs to knowPostpartum: Your Body
- Swelling: feet, ankles, hands, facePregnancy: Your Body
What mothers here say about D-dimer
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Sources
- Royal College of Obstetricians and Gynaecologists — Green-top Guideline 37a: Thromboprophylaxis during pregnancy, labour and after vaginal delivery, 2015
- American College of Obstetricians and Gynecologists — Practice Bulletin 196: Thromboembolism in Pregnancy, 2018