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Increase in vaginal discharge could be one of the effects caused by the emergency contraceptive use as they contain high doses of hormones. Wait and watch for withdrawal bleeding which should occur within 5-7 days of taking the pills. If the symptoms are associated with itching, burning, altered smell and consistency of discharge etc, then it would sagest possibility of infection.
Visit your gynecologist for examination and further management as indicated by examination and test results.
Take care.