Efficiency and efficacy of vitrification in 35 654 sibling oocytes from donation cycles.

Is oocyte vitrification/warming as efficient and effective as using fresh oocytes in donation cycles? IVF with vitrified donor oocytes is less efficient than using fresh oocytes, but its efficacy remains comparable to that of fresh cycles. Oocyte vitrification is used to preserve the reproductive potential of oocytes. A small number of randomized controlled trials carried out by experienced groups have shown that this technique provides fertilization, pregnancy, implantation and ongoing pregnancy rates comparable to those of fresh oocytes. However, large registry-based analyses have consistently reported lower live birth rates (LBRs) in cycles using vitrified oocytes. It is not clear whether this decrease may be due to the effect of vitrification per se on the oocytes or to the lower efficiency of the technique, as some of the oocytes do not survive after warming. Retrospective cohort analysis of 1844 cycles of oocyte donation (37 520 oocytes), each donor in the study provided enough oocytes for at least one reception cycle with fresh oocytes (2561 cycles) and one reception cycle with vitrified oocytes (2471 cycles) from the same ovarian stimulation (sibling oocytes). Overall, 35 654 oocytes were considered in the analysis. All embryo transfers (n = 5032) were carried out between 2011 and 2017. Differences in reproductive outcomes after the first embryo transfer were evaluated using Pearson's Chi-squared test and regression analysis adjusted for recipient's age, BMI, sperm origin and state, day of embryo transfer, morphological score and number of transferred embryos. We performed two additional sub-analyses, to test whether the efficiency and/or effectiveness of vitrification/warming impacts reproductive results. One analysis included paired cycles where the same number of fresh and vitrified oocytes were available for ICSI (SAME sub-analysis), while the second analysis included those cycles with a 100% survival rate post-warming (SAME100 sub-analysis). Baseline and cycle characteristics of participants were comparable between groups. Overall, fertilization rates and embryo morphological scores were significantly lower (P < 0.001) when using vitrified oocytes; moreover, vitrified oocytes also resulted in lower reproductive outcomes than sibling fresh oocytes using both unadjusted and adjusted analyses: ongoing pregnancy (32.1% versus 37.5%; P < 0.001; OR 0.88, 95% CI 0.77, 1.00) and live birth (32.1% versus 31.9%; P = 0.92; OR 1.16, 95% CI 0.90, 1.49). However, when the efficiency of warming was taken into account, reproductive outcomes in recipients became comparable: ongoing pregnancy (33.5% versus 34.1%; P = 0.82; OR 1.11, 95% CI 0.87, 1.43) and LBR (32.1% versus 32%; P = 0.97; OR 1.15, 95% CI 0.89, 1.48). Moreover, after selecting only cycles that, in addition to having the same number of oocytes available for ICSI, also had 100% post-warming survival rate in the vitrified group, reproductive outcomes were also comparable between fresh and vitrified oocytes: ongoing pregnancy (34.8% versus 32.4%; P = 0.42; OR 1.32, 95% CI 0.98, 1.77) and live birth (32.9% versus 31.0%; P = 0.52; OR 1.27, 95% CI 0.95, 1.71), indicating that reproductive outcomes of these cycles are affected by the efficiency of the vitrification/warming technique performed rather than the oocyte damage due to the fast cooling process to which oocytes are subjected. An open vitrification system was used for all cases, and oocyte vitrification/warming was performed by experienced embryologists with consistently high survival rates; caution must be exerted when extrapolating our results to data obtained using other open vitrification systems, closed vitrification systems or to IVF units with survival rates <90%. This is the largest cohort study comparing reproductive outcomes of vitrified and fresh sibling donor oocytes to date. We found that, when the number of oocytes available after warming is equal to the number of fresh oocytes, reproductive results including live birth are comparable. Consequently, the efficiency of vitrification must be taken into account to achieve the same reproductive outcomes as with fresh oocytes. We recommend implementing strict indicators of vitrification/warming efficiency in clinics and refining vitrification/warming protocols to maximize survival. This work was supported by intramural funding of Clínica EUGIN and by the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia (GENCAT 2015 DI 048). The authors declare no conflicts of interest. N/A.

Cornet-Bartolomé D ，Rodriguez A ，García D ，Barragán M ，Vassena R ... -  《-》

Definition of a clinical strategy to enhance the efficacy, efficiency and safety of egg donation cycles with imported vitrified oocytes.

Which is the most suitable clinical strategy in egg donation IVF cycles conducted with imported donated vitrified oocytes? The importation, and allocation, of at least eight vitrified eggs per couple during an egg donation cycle is associated with a high cumulative live birth delivery rate per cycle, as well as the confident adoption of a single blastocyst transfer strategy to minimize the risk of multiple pregnancies. IVF using donor eggs is commonly used worldwide to treat women who are unable to conceive with their own oocytes. In 2014, the Constitutional Court (n.162/2014) gave permission for gamete donation to be allowed for ART in Italy. Initially recommended as a therapeutic approach for premature ovarian insufficiency, the use of donated oocytes has become more and more common. In countries such as Italy, fresh oocyte donation is theoretically possible, but practically impossible due to the lack of donors. In fact, the Italian law does not allow reimbursement to the young women, who can only voluntarily donate their eggs. Therefore, Italian IVF centers have established several collaborations with international oocyte cryo-banks. The most popular workflow involves the importation of donated oocytes that have been vitrified. However, recent evidence has questioned the overall efficacy of such an approach. This is because detrimental effects arising from oocyte vitrification and warming might reduce the number of eggs available for insemination, with a consequential reduction in the achievable live birth rate per cycle. This was a longitudinal cohort study, conducted between October 2015 and December 2018 at two private IVF centers. Overall, 273 couples were treated (mean maternal age: 42.5 ± 3.5 years, range: 31-50 years; mean donor age: 25.7 ± 4.2, 20-35 years) with oocytes purchased from three different Spanish egg banks. We performed an overall analysis, as well as several sub-analyses clustering the data according to the year of treatment (2015-2016, 2017 or 2018), the number of warmed (6, 7, 8 or 9) and surviving oocytes (≤4, 5, 6, 7, 8 or 9) and the cycle strategy adopted (cleavage stage embryo transfer and vitrification, cleavage stage embryo transfer and blastocyst vitrification, blastocyst stage embryo transfer and vitrification). This study aimed to create a workflow to maximize IVF efficacy, efficiency, and safety, during egg donation cycles with imported vitrified oocytes. The primary outcome was the cumulative live birth delivery rate among completed cycles (i.e. cycles where at least a delivery of a live birth was achieved, or no embryo was produced/left to transfer). All cycles, along with their embryological, obstetric and neonatal outcomes, were registered and inspected. The survival rate after warming was 86 ± 16%. When 6, 7, 8 and 9 oocytes were warmed, 94, 100, 72 and 70% of cycles were completed, resulting in 35, 44, 69 and 59% cumulative live birth delivery rates per completed cycle, respectively. When ≤4, 5, 6, 7, 8 and 9 oocytes survived, 98, 94, 85, 84, 66 and 68% of cycles were completed, resulting in 16, 46, 50, 61, 76 and 60% cumulative live birth delivery rates per completed cycle, respectively. When correcting for donor age, and oocyte bank, in a multivariate logistic regression analysis, warming eight to nine oocytes resulted in an odds ratio (OR) of 2.5 (95% CI: 1.07-6.03, P = 0.03) for the cumulative live birth delivery rate per completed cycle with respect to six to seven oocytes. Similarly, when seven to nine oocytes survived warming, the OR was 2.7 (95% CI: 1.28-5.71, P < 0.01) with respect to ≤6 oocytes. When cleavage stage embryos were transferred, a single embryo transfer strategy was adopted in 17% of cases (N = 28/162); the live birth delivery rate per transfer was 26% (n = 43/162), but among the pregnancies to term, 28% involved twins (n = 12/43). Conversely, when blastocysts were transferred, a single embryo transfer strategy was adopted in 96% of cases (n = 224/234) with a 30% live birth delivery rate per transfer (N = 70/234), and the pregnancies to term were all singleton (n = 70/70). During the study period, 125 babies were born from 113 patients. When comparing the obstetric outcomes for the cleavage and blastocyst stage transfer strategies, the only significant difference was the prevalence of low birthweight: 34 versus 5%, respectively (P < 0.01). However, several significant differences were identified when comparing singleton with twin pregnancies; in fact, the latter resulted in a generally lower birthweight (mean ± SD: 3048 ± 566 g versus 2271 ± 247 g, P < 0.01), a significantly shorter gestation (38 ± 2 versus 36 ± 2 weeks, P < 0.01), solely Caesarean sections (72 versus 100%, P = 0.02), a higher prevalence of low birthweight (8 versus 86%, P < 0.01), small newborns for gestational age (24 versus 57%, P = 0.02) and preterm births (25 versus 86%, P < 0.01). This retrospective study should now be confirmed across several IVF centers and with a greater sample size in order to improve the accuracy of the sub-analyses. Single blastocyst transfer is the most suitable approach to achieve high success rates per procedure, thereby also limiting the obstetric complications that arise from twin pregnancies in oocyte donation programs. In this regard, the larger the cohort of imported donated vitrified oocytes, the more efficient the management of each cycle. None. None.

Rienzi L ，Cimadomo D ，Maggiulli R ，Vaiarelli A ，Dusi L ，Buffo L ，Amendola MG ，Colamaria S ，Giuliani M ，Bruno G ，Stoppa M ，Ubaldi FM ... -  《-》

How does vitrification affect oocyte viability in oocyte donation cycles? A prospective study to compare outcomes achieved with fresh versus vitrified sibling oocytes.

Solé M ，Santaló J ，Boada M ，Clua E ，Rodríguez I ，Martínez F ，Coroleu B ，Barri PN ，Veiga A ... -  《-》

Comparison of two different oocyte vitrification methods: a prospective, paired study on the same genetic background and stimulation protocol.

Can two different methods for oocyte vitrification, one using an open tool and the other a closed tool, result in similar oocyte survival rates? The oocyte survival rate was found to be higher in the closed method. Open vitrification is performed routinely in oocyte donation cycles. Closed oocyte vitrification may result in slower cooling rates and thus it is less used, even though it has been recommended in order to avoid the risk of cross-contamination between material from different patients. This is a prospective cohort study with sibling oocytes carried out in a fertility center between July 2014 and January 2016. The study included 83 oocyte donors each providing a minimum of 12 mature oocytes (metaphase II: MII) at oocyte retrieval. Oocyte survival rate and fertilization rate, as well as reproductive outcomes (biochemical, clinical, ongoing pregnancy and live birth rates) per embryo transfer and also cumulatively between the two methods were compared by Chi2 tests. Donor oocytes were denuded and six MII oocytes from each donor were vitrified using an open method and later assigned to one recipient, while another six MII oocytes were vitrified using a closed method and assigned to a different recipient (paired analysis). ICSI was used in all cases and embryo transfer was performed on Day 2-3 in all cases. Oocyte donors were 24.8 years old on average (SD 4.7). Recipient age (average 41.2 years, SD 4.7) and BMI (mean 23.8 kg/m2, SD 4.0) were similar between recipient groups. Oocytes vitrified using the closed method had higher survival rate (94.5% versus 88.9%, P = 0.002), but lower fertilization rate (57.1% versus 69.8%, P < 0.001) compared to the open method. The number of fresh embryos transferred in the two groups was 1.8 on average (SD 0.4). Biochemical (45% closed versus 50% open), clinical (40% versus 50%) and ongoing (37.5% versus 42.5%) pregnancy rates were not different between groups (P > 0.05) and neither were live birth rates (37.5% versus 42.5%, P > 0.05). Cumulative reproductive results (obtained after the transfer of all the embryos) were also similar between groups. The participants of this study were oocyte donors, i.e. young women in good health, and care should be exerted in extending our results to other populations such as infertility patients, oncofertility patients and women freezing oocytes to delay childbearing. Our results suggest that, in spite of different survival and fertilization rates, closed and open oocyte vitrification methods should offer similar reproductive outcomes up to cumulative live birth rates. The authors report no conflict of interest. Vitrolife provided the media and the closed method tool needed for the study at no cost.

Pujol A ，Zamora MJ ，Obradors A ，Garcia D ，Rodriguez A ，Vassena R ... -  《-》

Should we worry about the clock? Relationship between time to ICSI and reproductive outcomes in cycles with fresh and vitrified oocytes.

Is there an optimal time to perform ICSI with respect to the times of oocyte pick-up (OPU), in order to maximize the reproductive outcomes in cycles with fresh and vitrified/warmed donor oocytes? We found no significant differences in reproductive outcomes of ICSI cycles within a wide range of times between OPU and ICSI. In assisted reproduction, the oocyte is subject to denudation, vitrification/warming and ICSI. As shorter interaction with cumulus cells, oocyte ageing in vitro and insufficient recovery after warming may all impact the resulting embryo developmental competence, strictly controlled times between procedures are often implemented. However, most protocols have not been tested with the aim to improve reproductive results, and little information is available on the ideal times to be followed during these steps in order to optimize fertilization rates and embryo quality, and to achieve the highest pregnancy rate. Data from 3986 ICSI cycles performed between December 2012 and May 2014 were included (3178 with fresh and 808 with vitrified/warmed donor oocytes). ICSI was performed using donor oocytes and either partner or donor sperm. Exact times between OPU, denudation, vitrification, warming and ICSI were recorded automatically by a radiofrequency-based system. OPU was performed strictly 36 h after GnRH agonist trigger. Biochemical pregnancy was defined as a positive serum βHCG 15 days after transfer, clinical pregnancy was defined as a visible embryo with heartbeat 5 weeks after transfer, and ongoing pregnancy was defined as a normally developing pregnancy at 12 weeks after transfer. Times between OPU and ICSI (OPU-ICSI) ranged from 1 h 25 min to 17 h 13 min (averagefresh ± SD = 4 h 58 m ± 1 h; averagevitrified= 9 h 18 m ± 2 h). We found no effect of OPU-ICSI time on fertilization rate (pfresh=0.39; pvitrified=0.86) or embryo quality at Days 2 and 3 (pfresh=0.08; pvitrified=0.22). There was no difference in average OPU-ICSI times between positive and negative pregnancies (biochemical, clinical, ongoing and live birth rates) in either fresh (P = 0.71, 0.43, 0.79, 0.96) or vitrified (P = 0.59, 0.33, 0.73, 0.87) oocytes, respectively. Data were adjusted for oocyte donor age, semen status, number of motile spermatozoa and sperm concentration, and no effect of OPU-ICSI time on pregnancy and live birth rates for either fresh (P = 0.57, 0.16, 0.11, 0.46) or vitrified (P = 0.80, 0.73, 0.91, 0.95) oocytes was found. Further analysis for linear trend using OPU-ICSI time categorized in deciles showed that pregnancy rates and live birth rates do not increase or decrease across deciles. We found no effect of time taken for denudation to vitrification, warming to ICSI and denudation to ICSI on pregnancy rates. This is a study with automatically collected times from a high number of ICSI cases; however, its retrospective nature cannot exclude the influence of unaccounted for variables on the results. All oocytes came from oocyte donors (≤35 years old), so results cannot be extended to older or infertile women. Our results indicate that the effective window of time for insemination by ICSI might be wider than previously thought. It therefore appears that, within appropriate time frames, the management of ICSI cycles involving oocytes from young women in embryology laboratories could be adjusted to accommodate caseloads and workflow with no loss of oocyte viability or cycle efficiency.

Bárcena P ，Rodríguez M ，Obradors A ，Vernaeve V ，Vassena R ... -  《-》