to accomplish sterilization. The CREST study reported on a cohort of 10,685 women sterilized from 1978 to 1986 at any of 16 participating centers in the United States who were followed from 8 to 14 years (281). The true failure rates for 10 years obtained by the life-table method are given in Table 10.8. Pregnancies resulting from sterilization during the luteal phase of the cycle in which the surgery was performed were excluded. Of all remaining pregnancies, 33% were ectopic. The most effective methods at 10 years were unipolar coagulation at laparoscopy and postpartum partial salpingectomy, generally a modified Pomeroy procedure. Bipolar tubal coagulation and the Hulka-Clemens clip were least effective. The Filshie clip was not evaluated because it was not in use in the United States at the time. Younger women had higher risk for failure, as would be expected because of their greater fecundity.
Over the years since the CREST study began, sterilization by unipolar electrosurgery was abandoned because of the risk of bowel burns and was replaced with bipolar electro-surgery or the nonelectric methods (tubal ring, Hulka-Clemens clip, and the Filshie clip). An important later analysis of the CREST data found that bipolar sterilization can have a very low long-term failure rate if an adequate portion of the tube is coagulated. CREST study participants who were sterilized with bipolar electrosurgery from 1985 to 1987 had lower failure rates than those sterilized earlier (1978–1985). The important difference was in the application technique of the electric energy to the tubes. Women whose bipolar procedure involved coagulation at three sites or more had low 5-year failure rates (3.2 per 1,000 procedures), whereas women who had fewer than three sites of tubal coagulation had a 5-year failure rate of 12.9 per 1,000 (p = .01) (288).
Family Health International reported large randomized multicenter trials of the different means of tubal sterilization. The Filshie and Hulka clips were compared in two trials. A total of 2,126 women were studied, of which 878 had either clip placed by minilaparotomy and 1,248 had either clip placed by laparoscopy. The women were evaluated at up to 24 months (289). Pregnancy rates were 1.1 per 1,000 women with the Filshie clip and 6.9 per 1,000 with the Hulka clip at 12 months, a difference in rates that approached statistical significance (p = .06). This same group compared the Filshie clip with the Silastic tubal ring in a similar study with a total of 2,746 women, of which 915 had the devices placed at minilaparotomy and 1,831 at laparoscopy (290). Pregnancy rates at 12 months were the same for the Filshie clip and the tubal ring: 1.7 per 1,000 women. The ring was judged more difficult to apply. The Filshie clip was expelled spontaneously from the vagina by three women during the 12 months of follow-up.