yes, it can give a false negative.
However, it is an FDA category C medication. Studies have not been done in humans. However, animal studies have shown that amphetamines
may increase the chance of birth defects if taken during the early months of pregnancy
In addition, overuse of amphetamines during pregnancy may increase the chances of a premature delivery and of having a baby with a low birth weight
. Also, the baby may become dependent on amphetamines and experience withdrawal effects such as agitation and drowsiness