To analyze the effect of time intervals from the end of sperm collection to IUI on the pregnancy rates in couples who treated by COH–IUI cycles with gonadotropin due to unexplained infertility.

556 couples who underwent the first COH–IUI treatment with gonadotopin due to unexplained infertility were included. Semen samples were obtained by masturbation in a private room near the laboratory on the day of insemination. For each semen samples, time between the delivery time to the laboratory and starting time of sperm washing procedure was noted as semen collection to sperm washing (SC–SW) interval, the time between the starting time of sperm washing procedure and insemination time was noted as sperm washing to insemination (SW–IUI) interval and the time between the delivery time to the laboratory and insemination was noted as semen collection to insemination (SC–IUI) interval. Clinical pregnancy was defined as positive pregnancy test followed by the presence of an intrauterine gestational sac with fetal cardiac activity by transvaginal ultrasonography at least 4 weeks after IUI.

Among 556 couples, there were 84 cases of succesful clinical pregnancy and pregnancy rate was calculated as 15.1%. Intervals from SW to IUI and SC to IUI were significantly shorter in pregnant women than in non-pregnant (p<0.001 and p=0.007, respectively). SW performed ≤40min after SC resulted in higher clinical pregnancy rates than did SW performed >40min after SC (19.1% vs. 6.3%, respectively) (p<0.001). IUI performed ≤60min after the end of SW had higher pregnancy rates (16.9%) compared to IUI performed >60min after the end of SW (4.0%) (p=0.017). Likewise, IUI performed ≤90min after SC resulted in higher pregnancy rates than did IUI performed >90min after SC (18.9% vs. 12.0%, respectively) (p=0.029).

IUI outcome is enhanced by shorter intervals from SC to SW, from SW to IUI, and from SC to IUI in gonadotropin–IUI cycles for unexplained infertile couples.