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Cohort studies provide a measure of attributable risk, which is the difference in the incidence of disease between oral contraceptive users and non-users.
A barrier method such as condoms or spermicides must be used until the new ring has been used continuously for seven days.
This happened to me like a year ago I went to the Dr 5 days after heavy bleeding blood clots went through a box of half a bag of pads in one day it was so bad thought it was a misscarriage.