Medical Background
Tubal ligation is a surgical procedure in which the fallopian tubes are blocked, cut, or removed. It is often performed via a small abdominal incision (laparascopy, or postpartum minilaparotomy). It can also be performed during a cesarean section.
Tubal ligation works by preventing fertilization. When the fallopian tubes are cut or blocked, sperm cells are unable to reach the egg cell, and fertilization cannot take place.
Tubal ligation is usually permanent. In some cases, it can be surgically reversed; however, such surgery is complex and not always successful. Therefore, a woman should opt for tubal ligation only if she is certain that she wants to avoid natural conception for the rest of her life. (A woman who has had tubal ligation can conceive or carry a baby via IVF.)
Efficacy
Tubal ligation is 99.5% effective.
Halachic Considerations
As above, tubal ligation raises the serious halachic question of sterilization (sirus). Therefore, halachic consultation is essential for a woman considering it. Though the prohibition for women is rabbinic, halachic authorities generally permit tubal ligation only in very extenuating circumstances, where there is a compelling need for contraception and a woman cannot use permissible reversible methods.
Since the procedure can sometimes be reversed, although with variable success, authorities may sometimes rule more leniently. According to some authorities, there may be a preference for techniques of tubal sterilization that are more likely to be reversible.