Using an anticoagulant requires careful monitoring of the blood on a regular basis at any time, and if used when a woman is pregnant, her physician must be extra vigilant. There is a concern that some types of medication can cross the placenta and directly affect the baby, but low-molecular-weight heparin (LMWH), one type of anticoagulant, does not cross the placenta and is considered safe to use during pregnancy. It is important to note that there can still be concerns about excessive bleeding at the time of delivery, which is another significant consideration related to the use of an anticoagulant in pregnancy.
Many women have serious health issues that require treatment with anticoagulants, including concerns such as artificial heart valves, a history of deep vein thrombosis (DVT), or thrombophilia. In all of these situations the woman is at significant risk for the formation of potentially life-threatening blood clots, and the situation is often made worse by the stresses of being pregnant. For a woman with any of these problems, using an anticoagulant in pregnancy is likely to be essential to her survival.
It is important to limit the choice of the anticoagulant in pregnancy to those which have been shown to be safe for the baby, as some types have been found to cause birth defects or other physical or mental problems in both the fetus and the newborn baby. Warfarin is a common anticoagulant whose label warns that it is not safe to take during pregnancy, but it is not thought to be harmful to breastfeeding babies. In some cases the doctor may decide to use one type of anticoagulant early in the pregnancy, then switch to another type as the birth approaches.
Aside from concerns about the possibility of birth defects, the biggest concern related to the use of an anticoagulant in pregnancy is bleeding, prior to, during, or for a few weeks after the birth. Levels need to be closely monitored and patients should be watched carefully for any indications of internal bleeding. Some bleeding during pregnancy is normal, but in the case of a woman who is taking anticoagulants the bleeding may not stop, which can result in serious, possibly even fatal, consequences for her or for the baby.
Taking drugs in pregnancy always carries with it some risks, but in many cases it is safer to take drugs than to avoid them completely. This is true when considering the use of an anticoagulant in pregnancy, especially for women that are at risk for DVT or who have had several unexplained miscarriages, since these may actually be related to the formation of clots. Deep vein thrombosis can also become life-threatening if clots break loose and lodge in the lungs or other organs. The March of Dimes reports that a pulmonary embolus, which is a blood clot that has formed elsewhere in the body that travels to the lungs, is a leading cause of maternal death; the use of an anticoagulant in pregnancy can prevent this.