In our study, a relatively recent technique, the sperm chip technique, was compared to one of traditional approaches. The ICSI procedures were performed with males having normal semen analysis. Although use of sperm chip technique contributed to the development of good quality embryos reaching to the blastocyst stage, clinical pregnancy rates were not found to be significantly higher in the sperm chip group and use of this technique did not increase clinical pregnancy rate in the ICSI procedure.
There are several reports in the literature evaluating the factors that affect ART success. Clinical variables such as maternal age, total sperm count, total motile sperm count, sperm motility, embryo quality and sperm selection method are among these predictors of IVF/ICSI treatment success [9, 10].
Sperm chip is a technique developed as an alternative to other sperm preparation techniques and best imitates the natural sperm selection in the female genital tract. Sperm can be prepared with this method to use during intrauterine insemination (IUI), IVF and ICSI procedures. In other words, sperm chip technique was developed to imitate the female genital system and provide great convenience to clinicians, especially in male infertility cases and recurrent unsuccessful previous ART attempts [11–13]. A recent study by Ozcan et al showed that use of microfluidic sperm-sorting chip for sperm selection in infertile cases with male factor might improve IVF success rates .
For patients with oligozoospermia, ICSI is a vital technique since only a few sperm are adequate for the procedure. In ICSI, the process of oocyte selection is disregarded and fully left to the ICSI performer . As clinical success following ICSI depends on obtaining the most healthy and viable sperm cells, sperm chip technique enables to select sperm having the best DNA quality and being the least exposed to free oxygen radicals.
Another factor for predicting success is the sperm DNA Fragmentation Index (DFI). It was shown that high DFI is associated with failed pregnancies following IVF/ICSI cycles [16–18]. Although another study published later showed that high DFI had no effect on fertilization rate, quality of embryo or clinical pregnancy rate, it was indicated that spontaneous abortus rate was statistically higher in those with a DFI over 27% . It was also shown that DFI had little to no effect on fertilization and early embryo development. However, it had an obvious negative effect on blastocyst development phase and embryo implantation [20, 21]. When ejaculate is added into the sperm chip channels, sperm with the least DNA fragmentation will sort at the highest percentage and therefore will have the highest chance for fertilization . Thus, the most clinically usable, highly motile sperm with nearly undetectable levels of DNA fragmentation could be selected by sperm chip technique [4, 23]. It is possible to speculate that sperm chip technique may increase clinical pregnancy rate by eliminating negative effect of DFI by selecting healthy sperm. In other words, the number of good quality embryos that can reach the blastocyst stage was increased significantly by use of sperm chip technique. Success in obtaining good quality embryos with use of sperm chip technique may be explained by the lower exposure of the sperm to oxidant factors. In traditional methods, during processing of the sperm sample, the protocol may extend to 2 hours and this causes a prolonged exposure to the free oxygen radicals already produced as a result of the procedure. On the other hand, sperm chip technique that lacks centrifugation and is completed in one step protocol only takes 30–45 minutes . Reduced procedure time results in an important drop in the sample's exposure time to free oxygen radicals, enabling prevention of possible DNA damage .
One of the most important indications for the sperm chip technique use is recurrent IVF failures. Yildiz et al found a significant improvement in the fertilization rates in infertility patients who had previously failed more than twice in fertility treatment . In contrast, we did not obtain increased success regarding fertilization rate comparing to controls although our study population included the patients with previous failure histories rather than patients coming to our clinic for the first time.
Despite many existent studies showing the potential of sperm chip technique microscopically when it comes to sperm morphology, motility and DNA integrity, there are not many studies in which clinical pregnancy rates were reported [4, 6, 26, 27]. In a recent randomized controlled study with 122 patients, grade 1 embryo count was found to be significantly higher in sperm chip group, similar to our results. This study failed to show a significant difference in clinical pregnancy or live birth rates . Similarly, we found that use of sperm chip contributes positively to the quality of embryo to be transferred on the 5th day but did not increase the clinical pregnancy rate.
Relatively small sample size and the undetermined cumulative pregnancy rate per patient due to failed reaching of all the frozen embryos data (even if the total and transferred embryo counts were similar) are the main limitations of our study.
In addition, we did not investigate the effect of sperm motility on fertilization and clinical pregnancy rates because sperm motility might cause a potential bias favoring the sperm chip group. Thus, we included patients with similar sperm motility and we only found that the number of oocytes retrieved was a significant predictor of clinical pregnancy rates, even after adjusting multivariable regression models for potential confounders.