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How long off BC until it is ineffective?

Question for everyone. My girlfriend was off the pill for three days which she has been on for years and we had unprotected sex During that time about two weeks ago. She went back on the birth control after the third day(a day after we had sex). I did not ejaculate in her but she has had headaches for the past two days. Of course Google says this is a symptom of pregnancy. Would it be probable for her to get pregnant given the time span? How long off BC until it is ineffective?

Thanks for the help everyone
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replied January 31st, 2015
Welcome to the ehealthforum and I am glad to help you out.

Since your girlfriend had missed three birth control pills and you had unprotected intercourse during that time, chances of pregnancy are there.

If you are apprehensive regarding the status of your girlfriend's pregnancy she can get it checked. Most home pregnancy tests that check urine beta-HCG are sensitive to 20-25 mIU/ml of HCG. The test can be positive anywhere from about 2-3 days prior to a missed menses to 4-5 days after, but usually it should be done 7-10 days past her missed period.

Otherwise you can get a serum HCG also done which is more specific than urine pregnancy test.
I sincerely hope that helps. Take care and regards.
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