As with any other type of contraceptive and birth control, there is no such thing as one hundred percent effectiveness rate. You can still get pregnant, but the liklihood is lessened.
If you missed doses, took antibiotics while on Ortho-Cept, or if you became violently ill with diarrhea or vomiting while on Ortho-Cept, it may not have been effective that month.
While regular administration of oral contraceptives confers good protection against pregnancy, some women do become pregnant while faithfully taking their medication. The risk of this is about 1%.
You would need to ask your doctor sbout that fact, they can tell you better about the chances of getting pregnant on it. Or if you can get pregnant while taking it.
