A plastic blade is a useful novel device in cryopreservation of vitrified human embryos.

Purpose To determine whether embryos cultured with a low oxygen level (2%) brought about beneficial effects on the outcome of ART. Methods This is a sequential case-control embryo-culture study. Embryos were cultured either with a gas mixture containing 2% O 2 , 5% CO 2 , and 93% N 2 (low-oxygen group) or 5% O 2 , 5% CO 2 , and 90% N 2 (conventional group). From January 2008 to September 2008, 873 fertilized oocytes were obtained from 250 patients in the lowoxygen group and from October 2008 to March 2009, 730 fertilized oocytes were obtained from 213 patients in the conventional group. The outcomes of ART were compared between two groups. Results The cleavage rate in the low-oxygen group (94.4%) was similar to that (94.7%) in the conventional group. The mean number of blastomeres on Day 3 in the low-oxygen group (mean ± SE) was 6.5 ± 1.9, and this was significantly lower than in the conventional group (6.8 ± 1.9, p \ 0.05). Moreover, the low-oxygen group produced worse quality embryos, on the basis of the significantly higher embryo grade 2.1 ± 0.6 versus 1.9 ± 0.6, p \ 0.001, in 5% oxygen. The pregnancy and miscarriage rates in the low-oxygen group were 22.3 and 20.8%, respectively, which were statistically similar to the outcomes in the conventional group. Conclusions Overall, culture of embryos at the low oxygen level did not significantly improve ART results compared with embryos grown in 5% oxygen. The study suggests that a low oxygen level worsens embryo morphology but does not impair embryo viability.

Purpose Hyaluronan-enriched transfer medium (HETM) could improve the clinical pregnancy rate (CPR) for patients with repeated implantation failures (RIF). In contrast, there have been seldom reports addressing the potentially beneficial effects of HETM for morphologically poor blastocysts (MPBLs). Our study aimed to evaluate whether the use of HETM would improve the CPR for the patients who were transferred with euploid MPBLs. Methods Patients who underwent single euploid blastocyst transfer between July 2020 and June 2022 were enrolled. We included only those blastocysts confirmed as euploid by PGT-A, and those blastocysts were transferred after thawing. The natural ovulatory cycle or hormone replacement cycle (HRC) protocol were used for endometrial preparation for frozen embryo transfer (FET). A total of 1,168 FET cycles were performed in the study period, including 954 cycles of morphologically good blastocysts (≥ 4BB in Gardner’s classification), and 85 cycles of MPBLs, of which 47 were transferred using HETM in FET (the HETM group), and the remaining 38 were transferred with the medium without hyaluronan (the control group). We compared the CPR between these two groups. Results The characteristics of patients were similar between the HETM and control groups. The CPR in the HETM group was significantly higher than the control group (47.4% and 21.5%, respectively, p = 0.019). The multiple logistic regression analysis found that the use of HETM was a predictive factor of positive pregnancy outcomes (OR = 5.08, 95% CI = 1.62–16.0, p = 0.019). Conclusion Our data suggests that HETM used in the euploid blastocyst transfer can improve the clinical pregnancy rates of morphologically poor blastocysts.

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