STERILIZATION

in medicine, surgical procedure for the permanent prevention of conception by removing or interrupting the anatomical pathways through which gametesi.e., ova in the female and sperm cells in the maletravel. The oldest form of surgical sterilization, tubal ligation, remains one of the most widely used; as originally performed, this consisted of tying the female's fallopian tubes closed with silk thread. Simple ligation has a high failure rate, however, and current procedure is usually combined with crushing or severing a section of the tubes, making the possibility of reopening the pathway remote. Tubal closure may also be achieved by electronic coagulation of a segment of the tubes or by chemical adhesives. Finally, occlusive devicesclips or bands of metal or some other materialmay be used to close the tube. Techniques involving clips and bands are less destructive to the uterine tubes and generally have higher reversal rates than other methods. Tubal sterilization can be performed through an open incision or endoscopically. Male sterilization (vasectomy) involves less risk to the subject and is simpler and less expensive than sterilization in women. In this procedure, each vas deferens, through which male sperm is transmitted, is severed through a small incision in the scrotum. This method has gained in use since the 1950s and is now the most common procedure for permanent sterilization in many countries. (See vasectomy.) Because a sterilized individual may at some point desire restored fertility, the chief drawback of sterilization as a contraceptive means has been its irreversibility. Using microsurgical techniques developed in the 1970s, some tubal closures have been reversed, but the procedure is difficult and expensive. It has had only limited success at restoring fertility, because other damage associated with the original sterilization may prevent successful conception. Surgical reversal of vasectomy has been somewhat more successful, achieving success about 80 percent of the time, but the conception rate following such reversal remains low.