An epidemiologic study of risk factors associated with pregnancy following female sterilization.

Data on 14,700 female sterilization patients were collected by the International Fertility Research Program (IFRP) from 1972 to 1978 and analyzed to determine risk factors associated with the incidence of pregnancy following sterilization. With a case-control approach, it was found that younger patients (less than or equal to 34 years old) and those who did not lactate after sterilization had a higher risk of becoming pregnant. Patients who were sterilized in the early phases of a service program had a higher risk of pregnancy than those sterilized later. In the laparoscopic series, the relative risk of pregnancy was four times greater in patients who had the prototype spring clip than in patients who had the Falope ring. The relative risk increased to 7.0 when patients who had the prototype spring clip were compared to those who had the Falope ring, electrocoagulation, or the Rocket clip. Patients sterilized by electrocoagulation had a low pregnancy risk, but the risk of an ectopic pregnancy was significantly higher than for those sterilized with mechanical devices. In the culdoscopic series, the tantalum clip had an unacceptable pregnancy risk.