Can a low dosage of vyvanse (lisdexamfetamine) cause miscarriage?

Probably not. There are no controlled studies of antidepressants in pregnancy, which would compare them to women who are pregnant and not on the medication, so to my knowledge, there is no good research to say one way or the other. In my practice, in my reading of the research, about one fifth of pregnancies end in miscarriage, so it's very difficult to tell what the causes are. Talk to your OB.