Blood Home > Lovenox and Pregnancy

The FDA has assigned a pregnancy Category B classification to Lovenox (enoxaparin), meaning that it is generally considered safe for pregnant women to take this medication. Animal studies indicate that even high doses of this medicine did not increase the risk of birth defects. Also, the drug does not cross the placenta, so it is not expected to cause problems for a developing fetus.

Is Lovenox Safe During Pregnancy?

Lovenox® (enoxaparin sodium) is a prescription medication approved to treat and prevent blood clots in certain situations (and also to prevent certain complications after heart attacks or other similar "cardiac events"). It is generally thought that this medication is safe for use during pregnancy.

What Is Pregnancy Category B?

The U.S. Food and Drug Administration (FDA) uses a pregnancy category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category B is given to medicines that have not been adequately studied in pregnant humans, but do not appear to cause harm to the fetus in animal studies. Medications that have been shown to be safe for use in pregnancy in humans (but have caused problems in laboratory animals) are also given a Category B rating.
This medication is thought to be safe for use during pregnancy for several reasons. In animal studies, Lovenox did not increase the risk of birth defects, even at very high dosages. Also, Lovenox does not cross the placenta (to the developing fetus) in humans, so it is not expected to increase the risk of bleeding in the fetus. Lastly, studies that looked at this use of Lovenox in pregnant women generally show that the drug does not appear to cause any significant problems (other than the usual risks with Lovenox that may occur in any individual).
Pregnant women cannot take warfarin (Coumadin®, Jantoven®), the oral anticoagulant, as it can cause numerous, serious problems (see Coumadin and Pregnancy). Therefore, heparin or low molecular weight heparin medications (like Lovenox) are preferred during pregnancy. In most cases, Lovenox is thought to be at least as safe and effective as regular heparin for use during pregnancy. However, it is still unclear if Lovenox is effective enough (compared to heparin) for preventing or treating clots in pregnant women with mechanical heart valves.
It should be noted that pregnant women probably should not take Lovenox from a multi-dose vial, as this product contains benzyl alcohol as a preservative. Benzyl alcohol crosses the placenta and can cause serious problems in premature newborns. The more commonly used single-dose prefilled syringes contain no benzyl alcohol.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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