Blood is a bodily fluid that is oxygenated by the lungs, pumped by the heart, and delivered to various parts of the body through the blood vessels. Blood is made up of red blood cells, white blood cells, platelets and plasma. Blood not only acts as a carrier of life-giving oxygen and essential nutrients, it is also involved in various vital bodily processes. Coagulation of blood is one such protective mechanism that the body employs for healing injuries and preventing severe blood loss. Besides the platelets, a protein called fibrin plays an important role in the coagulation of blood. The process of blood clotting involves the conversion of fibrinogen, a protein found in the blood plasma, into an insoluble protein called fibrin. It is fibrin that forms a mesh of strands in order to form a blood clot at the site of injury. At the same time, the body employs another mechanism (initiated by an enzyme, thrombin) to prevent the blood clots from becoming too big. It is during the process of degeneration of blood clots by a protein called plasmin that the cross-linked D fragments of fibrinogen protein are found in the blood. D-dimer is the medical term that is used to refer to these protein fragments. So, the elevated d-dimer levels in blood are basically indicative of thrombin activity. In this article, we will try to find out about the possible reasons behind the changes in d-dimer levels in pregnancy.
D-Dimer Concentrations in Normal Pregnancy
As mentioned earlier, d-dimer is basically a fibrin degradation product that is formed as a result of degradation of fibrin. Whenever, a blood clot forms in the body, thrombin activates the fibrinolytic system, thereby dissolving the blood clot. This is the reason why doctors usually order the d-dimer blood test whenever a patient seems to be exhibiting the symptoms of blood clotting disorders such as deep-vein thrombosis, arterial embolism or even a stroke. Though d-dimer levels can get elevated due to inflammation, infection or vascular injuries, changes in d-dimer concentration are not uncommon during pregnancy. This is due to the various physiological changes that take place during pregnancy.
The fetus receives the nutrients from the mother's blood and the heart works harder to meet the demands. The increase in the circulating volume of the blood increases the risk of bleeding and the formation of blood clots. Conditions such as gestational hypertension, preeclampsia and placental problems during pregnancy can also cause changes in the coagulation system which is why the levels of d-dimer may be higher than the d-dimer normal range of 0.50 mg/L. D-dimer test may also be ordered when Venous Thromboembolism (VTE) is clinically suspected during the course of pregnancy.
When is D-Dimer Blood Test Ordered?
As mentioned earlier, d-dimer test can help in the detection of disorders associated with the coagulation system of the body. Venous thromboembolism, which refers to the formation of blood clot within the veins, is one such condition that can affect pregnant women. Deep vein thrombosis is another serious medical condition that is associated with the development of blood clots in the deep veins located in the legs. Swelling in legs, leg pain and tenderness in the affected leg are some of the symptoms of deep vein thrombosis. Blood clots can also get lodged in arteries. Pulmonary embolism is another life-threatening condition wherein a blood clot gets lodged in the arteries that supply blood to the lungs. While some women may be genetically predisposed to this condition, women who are obese or are suffering from poor blood circulation in the veins are also at an increased risk of developing blood clotting disorders during pregnancy.
Pregnancy-related risks are also higher if women are in late 30s or 40s. Blood clotting disorders can pose serious risks to the mother and child which is why there's a great need to diagnose and treat them at an early stage. When doctors feel that the patient is exhibiting symptoms of such disorders, they may order d-dimer test. However, this test should not be viewed as the sole determining factor in case of pregnant women. Changes in d-dimer levels are often seen in normal pregnancies and doctors may therefore conduct other diagnostic tests to confirm the diagnosis. A variety of laboratory tests that are included within the coagulation screening include thrombin time, Prothrombin Time (PT), fibrinogen, activated partial thromboplastin time, platelet count and specific coagulation factor tests. These tests are useful diagnostic tools when it comes to the detection of hematological problems.
On a concluding note, an increase in d-dimer levels during pregnancy is normal which is why elevated d-dimer levels cannot be taken as a conclusive proof of blood clotting disorders. Since fluctuations in d-dimer levels are commonly seen during pregnancy, medical experts believe that d-dimer test alone cannot help in the detection of thrombotic conditions. Experts believe that research must be conducted in order to determine the new diagnostic thresholds for d-dimer levels for the purpose of detecting blood clotting disorders during pregnancy.