Oocyte insemination techniques are related to alterations of embryo developmental timing in an oocyte donation model.

Because of the different intrinsic characteristics of the classic IVF and intracytoplasmic sperm injection (ICSI) techniques, the timing of zygote development can be influenced by the method of fertilization. However, there is no information about the relevance of the insemination procedure on embryo-quality parameters as measured through their developmental dynamics. The aim of this work was to determine if the insemination technique, IVF or ICSI, influences embryo developmental kinetics by examining 1203 embryos from 178 couples undergoing oocyte donation with IVF or ICSI. Using time-lapse information, this work calculated several developmental kinetic variables, from pronuclear fading (PNF) to expanded blastocyst, and also the proportion of optimal embryos in a best time range with a predicted higher implantation potential. Embryo development after ICSI was slightly faster than after IVF; however, when PNF, rather than time of insemination, was established as t0, the differences between the two procedures disappeared. The percentage of optimal embryos showed a trend towards higher values in IVF-derived embryos; however, the difference was not statistically significant. With these results and through the time-lapse monitoring system, it is concluded that it is the fertilization method which determines embryo developmental kinetics if insemination time is used as the starting point. A key step in assisted reproduction is the assessment of oocyte and embryo viability to determine the embryo(s) most likely to implant. Current embryo assessment strategies in clinical settings largely rely on embryo morphology and cleavage rates, and although these systems have been successful in improving pregnancy rates, their precision is far from ideal as they are based on visual information. In contrast, automated image analysis may add objectivity to the process of embryo selection and consequently, lead to an improvement in the implantation rates. Timing of zygote development can be influenced by the method of fertilization or by in-vitro culture conditions, so it has been suggested that the fertilization procedure influences the length of time elapsed between fertilization and the first cleavage. In this report, we show the results from using a time-lapse monitoring system to determine the timing of key events during embryo development both in IVF and ICSI. Due to the different intrinsic characteristics of the classic IVF and ICSI techniques, the selection of a critical time point is essential so as to maximize the differences between the two methods. For that reason, we searched for evidence in the data obtained from the image analysis for a link connecting embryo cleavage and the fertilization technique and also to find whether the kinetic of development derived from classic IVF or ICSI is also related to a predicted higher implantation.