Late period; Plan B Pill

Patient: Me and my girlfriend had unprotected sex and I did pull out in time but just to make sure she took the plan b pill and so now her period is three weeks late. Is she pregnant or do we wait?

Symptoms: Nothing

Doctor: Hello,thanks for contacting askthedoctor.comIt is seen that usually after the emergency contraception , the withd rawal bleed should start within 7 days. If she hasnt had her menses for last 3 weeks now then it is imperative to rule out pregnancy . please get a urine pregnancy test done . if the test is negative then she can wait for another week for her menses to resume as it could be a side effect of plan b.But first pregnancy has to be ruled out to ascertain contraceptive failure.I hope i have answered your query in detail.regards