Chances of Pregnancy after Vasectomy

Dear Ask The Doctor: I had a vasectomy 10 years ago, it was unsuccessful, so I had the second vasectomy now I find out my girlfriend is pregnant, is this really possible?

Dear Richard: It is possible! It may take as long as 12 weeks before sterility can be confirmed following vasectomy. Therefore any unprotected sexual intercourse during this 12 week window may result in pregnancy.