Outcomes of vitrified early cleavage-stage and blastocyst-stage embryos in a cryopreservation program: evaluation of 3,150 warming cycles.

To assess the outcomes achieved after Cryotop vitrification of both early cleavage and blastocyst-stage embryos and to determine whether the embryo developmental stage and embryo quality as well as the origin of the embryos (ovum donation cycles, patients' own oocytes) and the endometrial preparation for the embryo transfer had any effect on the final outcome. Observational study. Private university-affiliated IVF center. Women undergoing 3,150 warming cycles whose embryos were vitrified due to various reasons. Vitrification by the Cryotop open device. Delivery rate (DR) per warming cycle. Survival rate was 95% (5,722 out of 6,019 embryos). The percentage of intact embryos at warming showing 100% blastomere survival was 93% (95% CI 90.1%-95.3%) for day 2 and 95% (95% CI 94.3%-95.7%) for day 3; 3,057 embryo transfers were performed (3% cancellation rate). The DR/warming cycle was 32.5% (95% CI 30.9%-34.2%). Slight differences in survival rate were found [94.9% (95% CI 93.0%-96.8%) for day 2, 94.2% (95% CI 93.4%-94.9%) for day 3, 95.7% (95% CI 94.5%-96.9%) for day 5, and 97.6% (95% CI 96.9%-98.6%) for day 6]. Overall implantation, clinical pregnancy, ongoing pregnancy, and live birth rates per warming cycle were 35.5% (95% CI 33.5%-38.5%), 41.7% (95% CI 39.9%-43.4%), 32.6% (95% CI 31.0%-34.2%), and 38.1% (95% CI 36.4%-39.8%) respectively. The linear regression model considering embryo developmental stage, ovum donation or patient's own oocytes, and hormonal replacement therapy or natural cycle for endometrial preparation (odds ratio 1.179; 95% CI 0.912-1.277) showed no impact on the DR. Highly successful cryopreservation of all embryo developmental stages is possible with the use of the Cryotop system. There are no variables clearly exerting a negative effect on the survival and delivery rates.

Cobo A ，de los Santos MJ ，Castellò D ，Gámiz P ，Campos P ，Remohí J ... -  《-》

Outcome of cryotransfer of embryos developed from vitrified oocytes: double vitrification has no impact on delivery rates.

Evaluate the outcome of cryotransfer of embryos developed from vitrified oocytes. Retrospective cohort study. Private university-affiliated IVF center. Women undergoing warming cycles in which vitrified embryos were developed from vitrified or fresh oocytes. Vitrification by the Cryotop open device. Delivery rate (DR) per warming cycle. A total of 471 warming cycles of 796 vitrified embryos developed from vitrified oocytes (group 1) and 2,629 warming cycles of 4,394 vitrified embryos derived from fresh oocytes (group 2) were evaluated. Overall survival rates were 97.2% [95% confidence interval [CI] 95.9%-98.6%] vs. 95.7% [95% CI 94.9-96.4], respectively. DRs per warming cycle were 33.8% (group 1) and 30.9% (group 2). Double vitrification had no effect on DR (odds ratio [OR] 0.877, 95% CI 0.712-1.080). Confounding factors (ovum donation or autologous cycles; day-3 or blastocyst embryo transfer [ET]; natural or hormonal replacement therapy for ET; single or double ET; previous cycles, number of oocytes, doses of gonadotropins and E2 levels on the day of hCG) did not modify the effect of double vitrification on DR (OR 0.872, 95% CI 0.702-1.084). Vitrification at early cleavage or blastocyst stage of embryos obtained from previously vitrified oocytes has no effect on DR/warming cycle.

Cobo A ，Castellò D ，Vallejo B ，Albert C ，de los Santos JM ，Remohí J ... -  《-》

Outcomes of vitrified-warmed day-4 embryos after day-3 cleavage-stage biopsy.

The objective of this study was to compare the post-warming survival rates of biopsied and non-biopsied day-3 embryos vitrified on day 4 and to evaluate the clinical outcomes of following transfers. This study included 18 preimplantation genetic diagnosis (PGD) patients and 18 non-PGD patients treated between January 2005 and January 2009 who had not achieved live births during their fresh embryo-transfer cycles and whose surplus embryos were cryopreserved on day 4. The embryo survival rate after warming in the PGD and non-PGD groups was similar (53/59, 89.8% versus 55/64, 85.9%, respectively; difference of 3.9% 95% CI -7.3 to 13.4). Vitrified embryo-transfer cycles yielded no significant differences between PGD and non-PGD groups in implantation rates (12/46, 26.1% versus 9/47, 19.1%, respectively; difference of 6.9%, 95% CI -9.7 to 22.2), clinical pregnancy rates (11/18, 61.1% versus 9/18, 50%, respectively; difference of 11.1%, 95% CI -20.6 to 40.6) and live birth rates (9/18, 50% versus 6/18, 33.3%, respectively; difference of 16.7%, 95% CI -15.1 to 44.8). These results showed that, in PGD cycles, embryos can be vitrified effectively on day 4 after biopsy on day 3. The objective of this study was to compare the post-warming survival rates of biopsied and non-biopsied day-3 embryos that vitrified on day 4 and to evaluate the clinical outcomes of following transfers. This retrospective study included 18 preimplantation genetic diagnosis (PGD) and 18 non-PGD patients treated between January 2005 and January 2009 who had not achieved live births during their fresh embryo transfer cycles and whose surplus were frozen on day 4. After warming in frozen embryo-transfer cycles, embryo survival with respect to embryo grades, implantation, clinical pregnancy and live birth rates were compared. The embryo survival rate after warming in the PGD group was similar to the survival rate in the non-PGD group (53/59, 89.8% versus 55/64, 85.9%, respectively; difference of 3.9%, 95% CI -7.3 to 13.4, P=0.701). Frozen embryo transfer yielded no significant differences between PGD and non-PGD groups in implantation rates (12/46, 26.1% versus 9/47, 19.1%, respectively; difference of 6.9%, 95% CI -9.7 to 22.2, P=0.581), clinical pregnancy rates (11/18, 61.1% versus 9/18, 50%, respectively; difference of 11.1%, 95% CI -20.6 to 40.6, P=0.737) or live birth rates (9/18, 50% versus 6/18, 33.3%, respectively; difference of 16.7%, 95% CI -15.1 to 44.8, P=0.499). These results showed that, in PGD cycles, embryos can be vitrified effectively on day 4 after biopsy on day 3.

Kahraman S ，Candan ZN 《-》

Clinical outcomes following cryopreservation of blastocysts by vitrification or slow freezing: a population-based cohort study.

What are the clinical efficacy and perinatal outcomes following transfer of vitrified blastocysts compared with transfer of fresh or of slow frozen blastocysts? Compared with slow frozen blastocysts, vitrified blastocysts resulted in significantly higher clinical pregnancy and live delivery rates with similar perinatal outcomes at population level. Although vitrification has been reported to be associated with significantly increased post-thaw survival rates compared with slow freezing, there has been a lack of general consensus over which method of cryopreservation (vitrification versus slow freezing) is most appropriate for blastocysts. A population-based cohort of autologous fresh and initiated thaw cycles (a cycle where embryos were thawed with intention to transfer) performed between January 2009 and December 2011 in Australia and New Zealand was evaluated retrospectively. A total of 46 890 fresh blastocyst transfer cycles, 12 852 initiated slow frozen blastocyst thaw cycles and 20 887 initiated vitrified blastocyst warming cycles were included in the data analysis. Pairwise comparisons were made between the vitrified blastocyst group and slow frozen or fresh blastocyst group. A Chi-square test was used for categorical variables and t-test was used for continuous variables. Cox regression was used to examine the pregnancy outcomes (clinical pregnancy rate, miscarriage rate and live delivery rate) and perinatal outcomes (preterm delivery, low birthweight births, small for gestational age (SGA) births, large for gestational age (LGA) births and perinatal mortality) following transfer of fresh, slow frozen and vitrified blastocysts. The 46 890 fresh blastocyst transfers, 11 644 slow frozen blastocyst transfers and 19 978 vitrified blastocyst transfers resulted in 16 845, 2766 and 6537 clinical pregnancies, which led to 13 049, 2065 and 4955 live deliveries, respectively. Compared with slow frozen blastocyst transfer cycles, vitrified blastocyst transfer cycles resulted in a significantly higher clinical pregnancy rate (adjusted relative risk (ARR): 1.47, 95% confidence intervals (CI): 1.39-1.55) and live delivery rate (ARR: 1.41, 95% CI: 1.34-1.49). Compared with singletons born after transfer of fresh blastocysts, singletons born after transfer of vitrified blastocysts were at 14% less risk of being born preterm (ARR: 0.86, 95% CI: 0.77-0.96), 33% less risk of being low birthweight (ARR: 0.67, 95% CI: 0.58-0.78) and 40% less risk of being SGA (ARR: 0.60, 95% CI: 0.53-0.68). A limitation of this population-based study is the lack of information available on clinic-specific cryopreservation protocols and processes for slow freezing-thaw and vitrification-warm of blastocysts and the potential impact on outcomes. This study presents population-based evidence on clinical efficacy and perinatal outcomes associated with transfer of fresh, slow frozen and vitrified blastocysts. Vitrified blastocyst transfer resulted in significantly higher clinical pregnancy and live delivery rates with similar perinatal outcomes compared with slow frozen blastocyst transfer. Comparably better perinatal outcomes were reported for singletons born after transfer of vitrified blastocysts than singletons born after transfer of fresh blastocysts. Elective vitrification could be considered as an alternative embryo transfer strategy to achieve better perinatal outcomes following Assisted Reproduction Technology (ART) treatment. No specific funding was obtained. The authors have no conflicts of interest to declare.

Li Z ，Wang YA ，Ledger W ，Edgar DH ，Sullivan EA ... -  《-》

A prospective pilot study comparing fertilization and embryo development between fresh and vitrified sibling oocytes.

Siano L ，Engmann L ，Nulsen J ，Benadiva C ... -  《-》