Improvement of survival and fertilizing capacity of human spermatozoa in an IVF programme by selection on discontinuous Percoll gradients.

Two techniques for the separation of spermatozoa were compared: swim-up migration (SUM) and centrifugation on a discontinuous Percoll gradient (CPG). Their respective effects on sperm motility were analysed by computer-assisted videomicrography in either normal or asthenozoospermic groups. In both groups, there was no difference in any of the motion parameters between the two treatments after 1-h incubation. However, a clear difference was observed after 24 h when excellent motility was retained only in the CPG-treated group. A total of 350 ejaculates were produced by the husbands of women undergoing oocyte retrieval in an IVF programme. Spermatozoa were treated by CPG when the infertility was due to poor quality spermatozoa (n = 91), when there was a known previous history of semen infection (n = 73) or when frozen semen, originating from a donor, was used (n = 36). In all other cases (n = 150), spermatozoa were treated by SUM. The cleavage rates obtained were 32.2, 70.1, 60.9 and 68.6% respectively in the four categories. The clinical pregnancy rates per oocyte retrieval were 19.8, 31.5, 22.2 and 18.0% respectively. Forty-eight births occurred in the CPG group: 28 boys and 20 girls, all normal. We conclude that CPG is useful, both in cases of poor semen quality and in tubal infertility, in which the clinical pregnancy rate increased significantly from 18.0 to 31.5%.