The main purpose of prescribing Provigil is to help people fight their sleep disorders. Like with some other medicines, there has been no study performed on humans, to check whether it is safe to use during pregnancy. However, studies performed on animals have proved, that this medicine is not safe to use during pregnancy.
There is a system in the United States, which classifies the possible risks a medication can do to a fetus. Provigl is a category C medicine, which just means that there was no studies performed on humans, but it is potentially dangerous for animals.
Therefore, if you are about to have a baby, or thinking about having a baby in the future, consult your doctor for better understanding all risks and benefits in your particular case.