Osteoporosis Home > Fosamax and Pregnancy

While there have been no human studies that looked at Fosamax and pregnancy, animal studies suggest that the drug may cause problems for both the mother and the fetus, such as delayed delivery and low birth weight. However, animals do not always respond to medicines the same way that humans do. Your healthcare provider may still prescribe Fosamax during pregnancy if the benefits outweigh the risks.

Fosamax and Pregnancy: An Overview

Fosamax® (alendronate sodium) is a prescription medication approved to treat Paget's disease of the bone, as well as to treat and prevent osteoporosis. The medication may not be safe for use during pregnancy, although the full risks are not currently known. Studies in pregnant animals have suggested that Fosamax may cause problems.

Fosamax and Pregnancy Category C

The U.S. Food and Drug Administration (FDA) uses a category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category C is given to medicines that have not been studied in pregnant humans but that do appear to cause harm to the fetus in animal studies. Also, medicines that have not been studied in any pregnant women or animals are automatically given a pregnancy Category C rating.
When given to pregnant rats, Fosamax increased the risk of miscarriage and low birth weight. It also appeared to increase the risk of bone problems. In addition, Fosamax caused delayed delivery and other problems during delivery, presumably due to the low calcium levels the medication caused in the pregnant rats. Because Fosamax is incorporated into bone and slowly released from it over time, it is not known if the drug will cause problems in newly forming fetal bones.
However, it is important to note that animals do not always respond to medicines the same way that humans do. Therefore, a pregnancy Category C medicine may be given to a pregnant woman if the healthcare provider believes that the benefits to the woman outweigh any possible risks to the unborn child.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
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