Enoxaparin may be prescribed during pregnancy to reduce the risk of blood clots in women who are prone to this medical condition. This medication usually considered safe for use during pregnancy, and it is known for possibly preventing miscarriages resulting from blood clots, which is why it may be prescribed. The U.S. Food and Drug Administration (FDA) has placed it in Pregnancy Category B, because animal studies have shown no ill effects on the fetus or mother. Though adequate studies on humans have not been performed, this medication does not cross the placenta to the baby, so taking enoxaparin in pregnancy can be considered generally safe for humans. The main exceptions include administration to women who have a mechanical heart valve, and the use of the multi-dose vial, because these two variations have caused medical problems and even death in some pregnant women.
Pregnancy Category B is usually reserved for medications that have either been tested on animals and show no harmful effects or have shown harmful effects in animals but not humans during studies. In the case of enoxaparin, animal studies have not shown an increased danger of birth defects, even when the medicine is given in abnormally high doses. Though this medicine has not been studied widely in humans, researchers have reason to believe that it does not usually harm fetuses, because it does not cross the placenta. For this reason, enoxaparin in pregnancy may be prescribed by doctors who believe the benefit of stopping blood clots outweighs the medicine's minimal risks.
Some studies, however, show that certain women should not be prescribed enoxaparin in pregnancy. There have been reports of both fetal and maternal death in women with prosthetic heart valves who took this drug to stop clots, likely because this medication was not strong enough. Such women may be better off taking heparin, which is considered slightly more effective at preventing clots but not quite as safe to take during pregnancy. Doctors should weigh the pros and cons of each medication before prescribing one of these drugs.
Another possible danger of taking enoxaparin in pregnancy applies only to the multi-dose vials of this drug. This is because they contain the preservative benzyl alcohol, which is known for crossing the placenta to the fetus. The result is the possibility of medical issues after the birth of the baby, with gasping syndrome being one of the most common conditions. This tends to occur most in preterm babies and can be fatal. The single-dose syringes of this drug do not have benzyl alcohol, so women who plan to take enoxaparin in pregnancy should typically use this option.