All anticoagulants are generally contraindicated in situations in which the reduction in clotting that they cause might lead to serious and potentially life-threatening bleeds. This includes people with active bleeding conditions (such as gastrointestinal ulcers), or disease states with increased risk of bleeding (e.g., low platelets, severe liver disease, uncontrolled hypertension). For patients undergoing surgery, treatment with anticoagulants is generally suspended. Similarly, spinal or lumbar puncture (e.g., spinal injections, epidurals, etc.) carry increased risk so treatment is suspended prior to these procedures.<unk>  should not be given to people with heparin-induced thrombocytopenia until platelet count has improved or normalised.<unk>  is usually best avoided in people with protein C or protein S deficiency as these thrombophilic conditions increase the risk of skin necrosis, which is a rare but serious side effect associated with<unk> . Pregnancy<unk>  is contraindicated in pregnancy, as it passes through the placental barrier and may cause bleeding in the fetus;<unk>  use during pregnancy is commonly associated with spontaneous abortion, stillbirth, neonatal death, and preterm birth. Coumarins (such as<unk>  are also teratogens, that is, they cause birth defects; the incidence of birth defects in infants exposed to<unk>  in utero appears to be around 5%, although higher figures (up to 30%) have been reported in some studies. Depending on when exposure occurs during pregnancy, two distinct combinations of congenital abnormalities can arise. First trimester of pregnancy Usually,<unk>  is avoided in the first trimester, and a low molecular weight heparin such as enoxaparin is substituted. With heparin, risk of maternal haemorrhage and other complications are still increased, but heparins do not cross the placental barrier, so do not cause birth defects. Various solutions exist for the time around delivery. When<unk>  (or another 4-hydroxycoumarin derivative) is given during the first trimester—particularly between the sixth and ninth weeks of pregnancy—a constellation of birth defects known variously as fetal<unk>  syndrome (FWS),<unk>  embryopathy, or coumarin embryopathy can occur. FWS is characterized mainly by skeletal abnormalities, which include nasal hypoplasia, a depressed or narrowed nasal bridge, scoliosis, and calcifications in the vertebral column, femur, and heel bone, which show a peculiar stippled appearance on X-rays. Limb abnormalities, such as brachydactyly (unusually short fingers and toes) or underdeveloped extremities, can also occur. Common nonskeletal features of FWS include low birth weight and developmental disabilities. Second trimester and later<unk>  administration in the second and third trimesters is much less commonly associated with birth defects, and when they do occur, are considerably different from fetal<unk>  syndrome. The most common congenital abnormalities associated with<unk>  use in late pregnancy are central nervous system disorders, including spasticity and seizures, and eye defects. Because of such later pregnancy birth defects, anticoagulation with<unk>  poses a problem in pregnant women requiring<unk>  for vital indications, such as stroke prevention in those with artificial heart valves. According to the American College of Chest Physicians (ACCP),<unk>  may be used in lactating women who wish to breast-feed their infants. Available data does not suggest that<unk>  crosses into the breast milk. Similarly, INR levels should be checked to avoid adverse effects.
Warfarin
Palladin
Clopidogrel
Ticlopidine
Apixaban
Ticagrelor
Heparin
Dabigatran