Semen preparation by standard swim-up versus swim-up with test yolk buffer incubation in intrauterine insemination: a randomized study

In order to compare the standard swim-up semen preparation with and without test yolk buffer (TYB) incubation in intrauterine insemination (IUI), we conducted a prospective multicentre randomized trial. A total of 121 infertile couples with male factor (n = 52) or unexplained infertility (n = 69) was randomly assigned to two groups following ovulation induction. Semen was prepared by standard swim-up in group A (n = 64) and by swim-up followed by TYB incubation in group B (n = 57). A maximum of two IUI cycles was performed. A total of 104 cycles was performed in the swim-up group and 90 in the TYB group. Overall, 15 pregnancies were achieved in group A and 23 in group B, with an overall pregnancy rate of 24.8 and 50.0% per patient respectively (chi2(1), P < 0.05). In the male factor group, pregnancy was achieved in six out of 24 couples (25%) following standard swim-up and in six out of 28 (21.4%) following swim-up and TYB incubation (chi2(1), not significant). In the unexplained infertility group, pregnancy was recorded in nine out of 40 couples (22.5%) following standard swim-up and in 17 out of 29 couples (58.6%) following swim-up and TYB incubation (chi2(1), P < 0.05).