Effects of sperm separation methods before intrauterine insemination on pregnancy outcomes and live birth rates: Differences between the swim-up and microfluidic chip techniques

Various sperm preparation techniques have been developed to obtain functionally, genetically and morphologically high-quality competent spermatozoa for use in assisted reproductive technologies, which may affect treatment options and thus pregnancy outcomes and live birth rates. We aimed to compare swim-up washing procedure (SWP) and microfluidics sperm sorting (MSS) with regard to sperm separation, pregnancy outcomes and live birth rates in infertile couples receiving intrauterine insemination. A total of 326 couples with unexplained infertility who underwent intrauterine insemination were enrolled in this retrospective cohort study and were divided into 2 groups according to sperm preparation technique. The MSS and SWP methods were used to prepare sperm in 178 and 148 patients, respectively. The median sperm concentration reduced significantly from 51 (30–100) million/mL to 20 (10–40) million/mL in the MSS group, and from 45 (26–80) million/mL to 25 (11–48) million/mL in the SWP group (both P < .001). Median motility increased significantly from 30.43 ± 17.79 to 57.48 ± 20.24 in the MSS, and from 32.89 ± 13.92 to 43.91 ± 20.11 in SWP (both P < .001). There was a difference between groups after preparation regarding sperm concentration (better with SWP) and motility (better with MSS) (P = .018 and P < .001, respectively). A total of 86 (26.4%) pregnancies were observed in participants and the clinical pregnancy rate was 23% in the MSS group and 30.4% in the SWP group (P = .133). Fifty-one infants were born alive and a great majority (n = 47) were delivered at term. Multivariate logistic regression analysis showed that higher duration of infertility was independently associated with lower live birth success (odds ratio: 0.811, 95% confidence interval: 0.662–0.996; P = .045). Other variables, including female age, type and reason of infertility, number of cycles, and sperm motility and concentration, were found to be nonsignificant (P > .05). We observed nonsignificant worse reproductive results using microfluid sperm selection in comparison to the pellet swim-up technique (live birth rate = 12% vs 20%). Our evidence is of limited quality due to the retrospective design of this study and sufficiently powered RCTs are needed to evaluate whether sperm selection based using a microfluidic chip is better, similar, or worse than the pellet swim-up technique.