Have you had one done this way?
According to this article on MSNBC:
"A tubal ligation is considered a fail-safe method of permanent contraception - or at least we used to think so. But recent studies have shown that of all women who have tubal ligations (done either at the time of C-section, immediately after a vaginal delivery or at another time through a laparoscopic procedure), 2 percent will get pregnant within 10 years."
Although it seems a fairly permanent way to ensure you will not become pregnant again, there are still risks.
I hope this answers your question.