Vitamin c can cause a miscarriage. can it cause one if the egg has not been fertilized yet or is being fertilized or will it help prevent pregnancy?

No, no, no, and no: Vitamin c does not cause miscarriages. Miscarriages happen frequently all over the world (to a big portion of natural pregnancies) and people take vitamin c every day, but the two things are unrelated. A woman cannot miscarry until after she is actually carrying (no such thing as miscarrying before or during fertilization). Vitamin c does not prevent pregnancy. Don't worry about eating oranges!