In pregnancy there is a more pronounced tendency for the blood to clot, the so-called hypercoagulable state. This is one of the so-called physiological, – natural changes in pregnancy, which prepare the body for the blood loss that occurs during childbirth.
Most pregnant women do not need routine testing for coagulation (so-called hemostasis). Normally, prothrombin time and activated partial thromboplastin time are usually normal or slightly reduced (shortened). D-dimers do not have high sensitivity and specificity during pregnancy and are a sign of an already formed clot in the body. They do not show where they come from.
Fibrin D-dimers are for the most part products of the breakdown of the clot (a blood clot that contains so-called fibrin). The normal plasma level of D-dimers with the ELISA test is < 500 ng / ml (measure unit FEU) or < 250 ng / ml (measure unit DDU). Increased plasma concentrations of D-dimers indicate recent or ongoing clotting in blood vessels and its subsequent breakdown, the so-called fibrinolysis.1
Non-pregnant woman* First trimester Second trimester Third trimester
D-dimer (mcg / mL) 0,22 to 0,74 0,05 to 0,95 0,32 to 1,29 0,13 to 1,7
aPTT (seconds) 26,3 to 39,4 23,0 to 38,9 22,9 to 38,1 22,6 to 35,0
| Gestation week | 2.5th percentile (90% CI) lower limit | 97.5th percentile (90% CI) upper limit |
| First trimester | 0.2 (200) | 0.9 (900) |
| Below<15. gestation week | (0.2-0.2) (200) | (0.8–0.9) (800-900) |
| Second trimester 15-27. gestation week | 0.2 (0.2-0.2) | 1.5 (1.4–1.6) |
| Third trimester > 27. gestation week | 0.4 (0.4–0.5) | 2.8 (2.6–3.1) |
Sensitivity of D-dimers (sensitivity to change detection)
False positive findings
Liver disease, high rheumatoid factor, inflammation, malignancy, trauma, pregnancy, surgery, advanced age.
False negative findings
If blood is taken shortly after a blood clot has formed and testing is delayed for several days, take anticoagulants.
The need for d-dimer haemostasis is determined based on the current pregnancy status associated with:
pregnant woman, related to thrombosis;
3. Obstetric history – data from possible previous pregnancies.
This is the starting point. The following is an interpretation of the result depending on the current state of pregnancy and the gestation week. A risk assessment is made – low, medium or high risk for venous thrombosis. On the other hand, there should be a reason to monitor haemostasis with D-dimers and a possible indication to monitor for the presence of congenital thrombophilia.
Non-obstetric causes (unrelated to pregnancy)
The D-dimer assay is clinically useful when suspected of: DVT (deep vein thrombosis), PE (pulmonary embolism), and DIC (disseminated intravascular coagulation).
D-dimers are not indicated in patients with moderate or high risk for DVT and PE, where prophylaxis is indicated on its own, and should only be taken as a control. D-dimers whose clinical picture is not related to DVT, PE or DIC are not indicated.
D-dimers are most useful in patients with a low chance for DVT or PE, where a negative result minimizes the possibility of DVT or PE.2
Obstetric causes
Placental lakes are present in about 2.2% (92 / 4,106) of cases. No statistically relevant difference was observed in birth weight, gestational age at delivery, unfavorable obstetric outcome and in macroscopic or microscopic changes between the control and examined groups.
CONCLUSION: Study data do not indicate an increased risk of adverse pregnancy outcome in cases where only placental lakes occur4
At 1,198 consecutive ultrasound examinations in the second trimester, placental lakes were detected in 17.8% of ultrasound examinations.
Detection of placental lakes is six times more likely with a thick placenta if it is more than 3 cm thick in the 20th week of gestation and if they cover more than 30% of the placental surface. It is associated with uteroplacental complications or an unfavorable pregnancy outcome. Lesions are more common with increasing placental thickness.5
Prevention of complications in pregnancy
Prevention of complications, such as preeclampsia, fetal growth retardation (growth retardation), premature placental abruption (abruption). Most of the available evidence does not support the association between inherited thrombophilia and complications. Prophylactic anticoagulant therapy to prevent preeclampsia, pregnancy loss, fetal growth restriction, or abruption in women with inherited thrombophilia is indicated in high-risk thrombophilia. One of the most common thrombophilias, MTHFR, is prevented by folic acid supplementation in PreMama Duo.
1. Patients with hereditary thrombophilia are at greater risk of thromboembolic complications during pregnancy due to pregnancy-related changes in several coagulation factors that are physiologically present in pregnancy.
2. The risk of thromboembolism is higher in patients who have a personal history and / or a confirmed family history of thromboembolic events.
3. Most large studies do not indicate a persistent association between inherited thrombophilia and adverse pregnancy outcomes in low-risk populations.
4. Routine testing for hereditary thrombophilia in women with a history of recurrent or irreversible fetal loss, abruption, intrauterine growth restriction, or preeclampsia is advised. There is evidence that the administration of anticoagulants does not improve the outcome of pregnancy in diseased patients.
5. It is recommended not to give prophylactic, anticoagulant therapy during pregnancy to prevent complications related to placental changes, if the fetus is of normal growth and development, with regular fetoplacental flows and a normal amount of amniotic fluid.
References
Weitz JI, Fredenburgh JC, Eikelboom JW . A Test in Context: D-Dimer SOJ Am Coll Cardiol. 2017;70(19): 2411-2420
Hoodwinker . Haematology .Content by Dr. Í. O’ Sullivan 31/01/2011
RCOG GUIDELINE-Green top guideline,No37a
Reis NS1, Brizot ML, Schultz R, Nomura RM, Zugaib M. Clinical uses of the D-dimer include evaluation for the following risk for an adverse pregnancy outcome in cases presenting with placental lakes .J Clin Ultrasound. 2005 Feb; 33(2):. 67-71
Thompson MO1, Vines SK, Aquilina J, Wathen NC, Harrington K .Are placental lakes of any clinical significance? Placenta. 2002 Sep-Oct;23(8-9):685-90
Practice Bulletin No. 138. American College of Obstetricians and Gynecologists. Obstet Gynecol 2013:122:706-17.
