A tubal ligation is when a woman's fallopian tubes are cut, burned or tied (or any combination thereof) in order to prevent her from conceiving again in the future. The failure rate of tubal ligation (the number of women who will become pregnant despite having had this procedure) is 1 in 1000 (or 0.1%), meaning that it is a highly effective form of permanent birth control.
Women and couples frequently choose to have a tubal ligation procedure so that they will not need to use any form of birth control in the future. The procedure is often performed at the time when the mother is giving birth, thus saving the need for an additional hospital visit. In addition to emotional aspects that the woman may not have considered prior to deciding to have a tubal ligation (e.g., the sudden feeling that she can no longer have a child - that that part of her life is over), life situations can change, making the woman and/or her partner feel that the decision was a mistake.
A tubal ligation can be reversed in a process known as tubal reversal, but reversals are only approximately 70% successful. The remaining 30% of women will only be able to conceive with the help of IVF - in vitro fertilization - an expensive medical procedure requiring a great deal of time and medical intervention, including egg retrieval usually performed under general anesthesia.
In conclusion, while tubal ligation is a procedure with a very high success rate, those considering it should do their best to consider all possible occurrences in the future before making their final decision. Many women have lived to regret their decision, particularly if it was made when they were very young (mid-20's).