Table of Contents
Introduction:
Some women require anticoagulation therapy during pregnancy and the postpartum period, including women with a history of venous thromboembolism, at high risk of deep vein thrombosis, prosthetic heart valves, left ventricular dysfunction, atrial fibrillation, or a history of fetal loss. Anticoagulant use during pregnancy is challenging because of its potential teratogenic (harm to the baby) effects, management of anticoagulation during the time of labor, and dosing complexities of the various agents. In addition, women receiving chronic anticoagulation who are planning to become pregnant require counseling about how to avoid the potential teratogenic effects of anticoagulant drugs and the passage of a few of the anticoagulants to the fetus.
What Are Anticoagulants?
Anticoagulants are a group of drugs that reduce the blood’s ability to clot. They break down existing clots or prevent the formation of new clots. Anticoagulants come in various forms, including medications that are taken by mouth, injections, and intravenous (IV) drugs. They are used for treating and preventing life-threatening conditions that can occur because of blood clots, like heart attacks, strokes, and pulmonary embolisms.
How Do Anticoagulants Work?
Our body is continuously balancing clotting and anti-clotting processes. If the blood does not clot properly, any injury can cause severe blood loss or, in some cases, even death. And if blood clots too much, it can lead to dangerous medical conditions. The clotting process stops bleeding, forms a protective layer to keep debris and germs out of a wound, and finally rebuilds the skin so it is good as new. Certain components in the blood keep the clotting processes in an inactive state. In this way, the body can activate them quickly when it is required.
The mechanism of action of anticoagulants is by interfering with the normal clotting processes. They undo or prevent coagulation, the process where the blood solidifies to form a clot. Depending on the anticoagulant type used, the disruption of the clotting process happens in different ways.
Are Anticoagulants Safe During Pregnancy?
Anticoagulation is indicated in women with DVT (deep vein thrombosis), PE (pulmonary embolism), and some heart conditions. Low-molecular-weight heparins (LMWHs), Unfractionated Heparin (UFH), and Warfarin have commonly used anticoagulants during pregnancy.
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Low-Molecular-Weight Heparins (LMWHs) - These are the first choice of drug for VTE (venous thromboembolism) treatment and prophylaxis in pregnancy. In pregnancy, studies have concluded that LMWH is effective and safe. The drug excretion in breast milk is minimal. LMWHs have lower rates of adverse effects when compared to UFH, including symptomatic osteoporosis (a condition causing the bone to become fragile and brittle), heparin-induced thrombocytopenia (deficiency in blood clotting agent leading to increased blood loss), bleeding, and allergic reactions.
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Warfarin - This should be avoided during pregnancy because it crosses the placenta and increases the risk of stillbirth, miscarriage, central nervous system abnormalities, embryopathy (nasal hypoplasia or stippled epiphyses), and maternal and fetal hemorrhage.
Why Are Anticoagulation Drugs Dangerous During Pregnancy?
If the anticoagulants are given during pregnancy, the complications should be explained before conception. The complication of anticoagulation drugs are:
1) Embryopathy - Warfarin is a commonly used anticoagulant drug because of its duration of action, predictable onset, and excellent bio-availability. It has the ability to freely cross the placenta and poses a risk of Warfarin embryopathy (developmental abnormality in the fetus), which happens in about 25 % to 30 % of cases, between 6 to 12 weeks. Embryopathy can be prevented if it has been withdrawn within six weeks of the last menstrual period. It can be replaced by parenteral anticoagulation drugs for 6 to 12 weeks of pregnancy. It should be withdrawn again at 36 weeks of pregnancy to avoid complications at the time of delivery.
Oral anticoagulants, when taken during the first trimester, may result in the failure of synthesis of matrix Gla-protein and osteocalcin, resulting in nasal hypoplasia (the fetal nasal bone appears smaller in sonography) and stippling. When anticoagulants are consumed during the second and third trimesters may lead to eye abnormalities and central nervous system abnormalities like optic atrophy, blindness, cataract, microphthalmia (a birth defect in which one or both eyes are not fully developed), microcephaly (a condition in which the size of the head of the baby is smaller than normal), hydrocephalus, intraventricular hemorrhage, seizures, growth retardation, and mental retardation. Anticoagulating drugs, when used during the postpartum period, do not affect the breastfed infant.
2) Fetal Loss - Spontaneous abortion is the most common fetal complication during pregnancy in women with mechanical heart valves. Both Heparin and oral anticoagulants carry this risk. This is because Warfarin inhibits the immature liver enzyme system of the fetus and results in a high risk of hemorrhagic complications and stillbirth. However, Heparin can not cross the placenta, but bleeding at the uteroplacental junction is possible. Warfarin can be replaced by heparin during the first trimester of pregnancy and can prevent malformations; however, this does not improve pregnancy outcomes.
3) Embolic Complications - Studies show that embolic complications were highest with low-dose Heparin than with subcutaneous Heparin and least with oral anticoagulation.
Which Anticoagulants Are Prescribed to Pregnant Women?
Anticoagulation in High-Risk Patients Before Childbirth:
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If the patient is taking Warfarin, it will be changed to UFH heparin infusion.
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The healthcare professionals may switch to an intermediate dose of subcutaneous LMWH or UFH, and it will be continued throughout pregnancy and after delivery.
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APTT (activated partial thromboplastin clotting time) and Anti-Xa will be monitored to achieve therapeutic levels of LMWH and UFH, respectively, every four weeks throughout pregnancy.
Management During Delivery or Labor:
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Subcutaneous UFH and LMWH will be stopped 24 hours before delivery.
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It will be restarted immediately after delivery if there is no postpartum hemorrhage.
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After two days, Warfarin started overlapping Heparin.
A thrombosis (serious health condition causing blood clots inside the blood vessels) risk assessment will be performed on all women undergoing C-sections to determine if thromboprophylaxis is required.
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In high-risk cases, anticoagulation therapy will be continued for at least six months.
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In low-risk cases, early mobilization or stocking is recommended after a C-section. Oral anticoagulation will be continued for at least six weeks post-delivery.
Conclusion:
Anticoagulation regimens are important during pregnancy and puerperium. Healthcare professionals may consider trimester-related preferences of anticoagulant drugs and special dose adjustments because of the teratogenic effect and complications that can be caused by specific anticoagulant drugs. The treatment will even be continued after delivery to avoid postpartum hemorrhage.
