Both Unfractionated heparin and low molecular weight heparin are approved for use during pregnancy. Heparins are good during pregnancy because they don’t cross the placenta. I.e. both LMWH and UFH don’t cross the placenta.
LMWH can be given SC at home.
UFH is only given IV.
As such, LMWH is the best choice for anticoagulation during pregnancy until the last few weeks. Unfractionated heparin is generally only recommended in the final weeks of the pregnancy because it can be rapidly reversed for delivery. Since it is given IV (unlike low molecular weight heparin which is administered subcutaneously), it is not feasible to maintain an individual on this therapy throughout a pregnancy.
The DOACs should be avoided during pregnancy because we don’t yet know about their safety.
Warfarin is contraindicated during pregnancy because we know it crosses the placenta, is a teratogen, and causes fetal anticoagulation throughout the pregnancy. Exposure during early pregnancy can result in embryopathy, while exposure later in pregnancy can cause fetal bleeding, including intracranial hemorrhage.
Indications for anticoagulation during pregnancy
Pregnancy is a hypercoaguable state, and anticoagulation during pregnancy is indicated for women with
-Atrial fibrillation,
-Mechanical valve prosthesis,
-Antiphospholipid antibody syndrome and
-venous thromboembolism.