From the Guidelines
Elevated D-dimer levels in pregnancy should be interpreted with caution, as they can be physiological and do not necessarily indicate venous thromboembolism (VTE), and a markedly elevated D-dimer level, several-fold above the upper range of normal for pregnancy, should be considered as indicative of coagulopathy. During pregnancy, D-dimer levels progressively increase each trimester, often exceeding the standard cutoff values used for non-pregnant patients 1. For this reason, healthcare providers should use pregnancy-specific D-dimer reference ranges when available, or consider using higher threshold values. If a pregnant woman has an elevated D-dimer level and symptoms concerning for VTE, such as leg swelling, chest pain, or shortness of breath, further diagnostic imaging is usually warranted despite the elevated D-dimer.
- Ultrasound for suspected deep vein thrombosis
- CT pulmonary angiography (with appropriate shielding) for suspected pulmonary embolism are preferred diagnostic tests. The elevated D-dimer in pregnancy occurs due to the normal hypercoagulable state of pregnancy, which involves increased clotting factor production and decreased anticoagulant activity to prepare for delivery 1. This physiological adaptation makes pregnant women 4-5 times more likely to develop blood clots compared to non-pregnant women, so clinicians should maintain a high index of suspicion for VTE despite the limited utility of D-dimer testing in this population. According to the most recent study, a markedly elevated D-dimer level should be considered as indicative of coagulopathy 1.
Some key points to consider:
- D-dimer levels are not reliable for excluding suspected PE in pregnancy due to their low specificity and the potential for false negatives 1
- The decision to refer for imaging evaluation should be based on clinical judgment and a high index of suspicion for PE
- Fetal radiation doses delivered in utero by properly performed diagnostic tests present no measurably increased risk of prenatal death, malformation, or impairment of mental development over the background incidence of these entities 1
From the Research
Implications of Elevated D-dimer in Pregnancy
- Elevated D-dimer levels during pregnancy indicate increased thrombin activity and fibrinolysis following fibrin formation, which may suggest a prothrombotic state 2, 3, 4.
- The increase in D-dimer levels is a normal physiological change during pregnancy, with levels increasing progressively and significantly through each trimester, peaking in the third trimester 5, 6.
- The use of D-dimer testing for diagnosis and prediction of venous thromboembolic events (VTE) or pregnancy-related complications is limited due to the substantial increase in D-dimer levels during normal pregnancy 3, 4, 6.
- Reference values of D-dimer according to gestational age need to be established to improve the clinical application of D-dimer testing during pregnancy 3, 5, 4, 6.
- Trimester-specific reference intervals for D-dimer levels have been established, with the following ranges: first trimester (169-1202 µg/L), second trimester (393-3258 µg/L), and third trimester (551-3333 µg/L) 5.
- Elevated D-dimer levels during pregnancy may require adjustment of low-molecular-weight heparin (LMWH) dosages to prevent thromboembolic events, with increasing doses needed to keep D-dimer levels within the normal range 2.