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.
Ambien is a category C drug.
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 at high doses, Ambien caused problems in bone formation of the fetal skull. When given to pregnant rabbits at high doses in early pregnancy, Ambien increased the risk of miscarriages and problems in bone formation. When given later in pregnancy (and during lactation), the medication decreased pup survival and growth. It should be noted that the high doses of Ambien used in these animal studies caused toxicity (such as poor weight gain) in the mothers. It is probably this toxicity that indirectly caused the problems for the fetuses, not the medication directly.
None of the animal studies suggested that Ambien caused birth defects.
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.
If you are pregnant or thinking about becoming pregnant, let your healthcare provider know. He or she will consider the benefits and risks of taking Ambien during pregnancy before making a recommendation in your particular situation.