Abstract
Background: Results from the latest meta-analysis, in fresh cycles, showed that the application of time-lapse monitoring (TLM) together with an embryo-evaluating algorithm was associated with a significantly higher rate of ongoing pregnancy and a lower rate of early pregnancy loss. The aim of this study was to compare the clinical outcomes of frozen embryos classified according to morphokinetic versus morphologic criteria.
 Methods: This was a retrospective cohort study, conducted at IVFAS, An Sinh Hospital, Vietnam, from July 2014 to July 2017. Patients undergoing in vitro fertilization (IVF) treatment with antagonist protocol and having freeze-only on day 5 were included. Exclusion criteria were patients (i) treated with in-vitro maturation, (ii) having obstructive azoospermia, or (iii) having uterine abnormalities. Embryos were cultured up to day 5 in TLM system (Primo Vision, Vitrolife, Sweden) or in benchtop (G185, K System, Denmark). The quality of frozen embryos was evaluated based on morphokinetic or morphologic criteria. In the subsequent cycle, endometrial preparation was done by using exogenous estradiol and progesterone. Embryos were thawed and up to 2 embryos were transferred to the uterus. The primary outcome was ongoing pregnancy. The rate of post-thaw survival, post-thawed good/moderate embryo, clinical pregnancy, implantation, miscarriage and ectopic pregnancy were used as secondary endpoints.
 Results: A total of 276 patients were recruited, with 138 patients in the morphokinetic group and 138 patients in the morphologic group. Baseline characteristics were comparable between the two groups. There was no significant difference in ongoing pregnancy rate in morphokinetic versus morphologic group (57.2% vs. 60.1%, p=0.71). All secondary outcomes were comparable between the two groups.
 Conclusion: In frozen day-5 embryo transfer, the clinical outcomes were similar when embryos were classified according to morphokinetic versus morphologic criteria for freezing. Using morphokinetic criteria to select embryos for freezing did not improve the ongoing pregnancy rate, as compared to morphologic criteria.
Highlights
Embryo culture, assessment and selection are important steps in improvement of the safety and efficacy in assisted reproductive technology
There was no significant difference in ongoing pregnancy rate in morphokinetic versus morphologic group (57.2% vs. 60.1%, p=0.71)
There were no significant differences between the two groups (Table 1)
Summary
Assessment and selection are important steps in improvement of the safety and efficacy in assisted reproductive technology. Embryo culture combined with time-lapse monitoring has become more popular worldwide and has created a new trend of in vitro fertilization [2,3,4]. It can maintain an optimal culture environment, and allow for the best possible culture conditions [5,6]. The aim of this study was to compare the clinical outcomes of frozen embryos classified according to morphokinetic versus morphologic criteria. Conclusion: In frozen day-5 embryo transfer, the clinical outcomes were similar when embryos were classified according to morphokinetic versus morphologic criteria for freezing. Using morphokinetic criteria to select embryos for freezing did not improve the ongoing pregnancy rate, as compared to morphologic criteria.
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