### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
Hi, I use Amethia Lo... the type of birth control where you only get periods a few times of year. Well I missed several doses and had unprotected sex, so I took Plan B, and now I am resuming my birth control as normal. My question is, will I have to wait till I get to the sugar pills to see if I had a period and to know it worked? Because I heard Plan B works by kind of flushing out your system, but if my BC is preventing periods, will it still work? Thank you! :(

### output:

Hi, Thanks for the query. Since you have used Birth control pills irregularly and also used plan B, it is difficult to predict when you will have a period. Even with this, in most cases, for women using birth control pills, periods will come only after the active pills are over despite using plan B in the middle of the cycle. Plan B works in more than 90% cases if taken properly. Concomitant use of both does not decrease the efficacy of plan B, and it still works. It works by delaying ovulation and changing the lining of the uterus to prevent pregnancy from occurring. It does not work if pregnancy has already occurred. The best way to know if you are pregnant in this case would be to take a pregnancy test at least 3-3 1/2 week after using plan B using a morning urine sample. If it is negative, chances of pregnancy resulting from the sexual act on that day [before you took plan B] are negligible. Another way to know is wait for your period while taking the sugar pills, if it is delayed a pregnancy test 7 days after the missed period will help. Hope you find this useful. Thanks for using Chat Doctor, and have a good day. ChatDoctor BagdeConsultant Obstetrician and Gynecologist