Improved semen qualities after continuous-step density gradient centrifugation: application to artificial insemination and pregnancy outcome.

For increasing sperm fertilizability in artificial insemination, it is effective to concentrate progressively motile sperm from whole ejaculate. We developed the continuous-step density gradient for the selective concentration of progressively motile sperm. The present procedure was applied to intrauterine artificial insemination. Infertile couples (n = 152) whose diagnoses involved oligoasthenospermia, cervical factor, and unexplained infertility were selected for artificial insemination with washed and concentrated sperm. Successful pregnancies (47) were obtained, with an overall pregnancy rate of 31% in the program. Sperm processing by this procedure improved pregnancy rates in couples with the sole diagnosis of oligoasthenospermia or cervical factor. In the patients in whom other fertility problems coexisted, however, it was essential to treat female fertility problems. Continuous-step density gradient centrifugation is effective in increasing the pregnancy rate in artificial insemination.