About POSTINOR POSTINOR is an Emergency Contraceptive Pill (ECP) which safely prevents unwanted accidental pregnancy within 72 hours after unprotected sexual intercourse. Why is POSTINOR unique? POSTINOR is effective to prevent pregnancy when taken as directed up to 72 hours (3 days) after unprotected sex. If you take POSTINOR it is 99% sure that you avoid pregnancy*.