Does taking birth control pills a few hours before sexual activity achieve contraceptive effectiveness?

Patient's question:

There is vomiting, lower abdominal pain

Doctor's answer:

Hello! Emergency contraception should be taken within 72 hours after sexual intercourse. Beyond 72 hours, the failure rate is often higher. Emergency contraception medication only works for the current act of unprotected sex. Even after taking medication during this cycle, other reliable contraceptive measures should still be used during sexual activity. If not taken properly, pregnancy may occur during the month of medication. Only one dose of emergency contraception should be used per menstrual cycle. The second dose will be ineffective. Emergency contraception should be taken under the guidance of a doctor.