Why does the pregnancy test still show positive after taking birth control pills?

Patient's question:

Taking birth control pills, no menstruation, pregnancy test shows two lines

Doctor's answer:

Two lines on a pregnancy test indicate pregnancy. It could be due to emergency contraception or successful breastfeeding. It is recommended to undergo a gynecological ultrasound for further confirmation. If your period is delayed and the early pregnancy test shows two lines, it means you are pregnant. Taking emergency contraception can lead to successful breastfeeding. Your current urine test is positive, indicating successful breastfeeding. The estimated time of pregnancy starts from the first day of your last menstrual period. You can confirm the size of the gestational sac through an ultrasound examination.