Markers of Oocyte Quality to Enhance Human IVF Outcomes: A Bibliographic Review

The markers of oocyte quality have remained a major controversy in the field of embryology due to the subjectivity of the different methods of oocyte assessment. Various scholars use oocyte quality and oocyte competence interchangeably. Oocyte quality can be defined as the overall health of an oocyte whereas oocyte competence refers to the ability of an oocyte to be fertilized and develop into a healthy embryo. Diminished oocyte quality is believed to be a result of alterations in oocyte growth and maturation processes that stem from several pelvic and systemic factors before and after oocyte retrieval. In this review, we focus on the morphological and nonmorphological markers of oocyte quality. Strict restrictions that limit the number of oocytes fertilized in various countries have triggered researchers around the world to come up with the most appropriate and noninvasive markers that enhance oocyte selection and optimize IVF outcomes. PubMed, Google Scholar, and the Cochrane Library were used to search for peer-reviewed, original articles about oocyte quality markers. The review was written in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Morphological markers are commonly used, but they are subjective, and no single marker can be used exclusively to predict oocyte competence and subsequent embryonic development potential. Furthermore, transcriptomics of differentially expressed genes in cumulus cells and assessment of metabolomics and other contents of follicular fluid have shown greater precision. However, their specificity to the different quality determinants needs further research.

Endogenous biosynthesis of docosahexaenoic acid(DHA)regulates fish oocyte maturation by promoting pregnenolone production

Omega-3 polyunsaturated fatty acids(n-3 PUFAs),particularly docosahexaenoic acid(22:6n-3,DHA),play crucial roles in the reproductive health of vertebrates,including humans.Nevertheless,the underlying mechanism related to this phenomenon remains largely unknown.In this study,we employed two zebrafish genetic models,i.e.,elovl2^(-/-)mutant as an endogenous DHAdeficient model and fat1(omega-3 desaturase encoding gene)transgenic zebrafish as an endogenous DHA-rich model,to investigate the effects of DHA on oocyte maturation and quality.Results show that the elovl2^(-/-)mutants had much lower fecundity and poorer oocyte quality than the wild-type controls,while the fat1 zebrafish had higher fecundity and better oocyte quality than wildtype controls.DHA deficiency in elovl2^(-/-)embryos led to defects in egg activation,poor microtubule stability,and reduced pregnenolone levels.Further study revealed that DHA promoted pregnenolone synthesis by enhancing transcription of cyp11a1,which encodes the cholesterol side-chain cleavage enzyme,thereby stabilizing microtubule assembly during oogenesis.In turn,the hypothalamic-pituitary-gonadal axis was enhanced by DHA.In conclusion,using two unique genetic models,our findings demonstrate that endogenously synthesized DHA promotes oocyte maturation and quality by promoting pregnenolone production via transcriptional regulation of cyp11a1.

Embryonic, genetic and clinical outcomes of fresh versus vitrified oocyte: A retrospective cohort study

Objective:To compare embryonic development,ploidy status and clinical outcomes between fresh and frozen-thawed oocytes.Methods:This retrospective cohort study evaluated 83 fertilization cycles including both fresh and frozen oocytes from 79 patients at the HP Fertility Center of Hai Phong International Hospital of Obstetrics and Pediatrics in Vietnam.The patient underwent several ovarian stimulation cycles to accumulate a certain number of oocytes that would be vitrified.In the last oocyte retrieval,all patient’s oocytes including both frozen and fresh would be fertilized.The outcomes included the rates of oocyte survival,cleavage embryo,blastocyst,ploidy status,pregnancy,biochemical pregnancy and clinical pregnancy.Results:The oocyte survival rate after thawing was 96.5%.No statistically significant difference was found when comparing fresh and frozen oocytes regarding fertilization rate(78.1%vs.75.5%,P=0.461),usable cleavage embryo rate(86.9%vs.87.2%,P=0.916)but usable blastocyst rate was found higher statistically in the frozen oocyte group(44.4%vs.54.0%,P=0.049).The percentages of euploid,aneuploid and mosaic embryos between the fresh group and the vitrified group had no significant differences(33.8%vs.31.6%,P=0.682;51.0%vs.54.2%,P=0.569;15.2%vs.12.4%,P=0.787;respectively).The rates of pregnancy,biochemical pregnancy and clinical pregnancy had no statistical difference(68.8%vs.64.8%,P=0.764;12.5%vs.3.6%,P=0.258;37.5%vs.46.4%,P=0.565).17 Mature oocytes are the minimum to have at least one euploid embryo.Conclusions:Oocyte vitrification does not affect embryonic,genetic and clinical results.The number of mature oocytes should be considered for fertilization in some cases.

Effect of Insulin-Transferrin-Selenium on Goat Oocytes Maturation and Embryo Development

[Objective] The research aimed to enhance culture efficiencies of oocyte and embryo of goat in vitro and to explore serum-free culture system in vitro.[Method] At present,the conventional solutions of oocyte maturation and embryo development in vitro were always added into 1% ITS(Insulin-transferrin-selenium) or using 1% ITS to replace FBS in 2 kinds culture solutions for conducting in vitro cultures of goat oocyte and parthenogenetic embryo.The influences of ITS on their developments were detected.[Result] ITS in maturation liquid of oocytes could not increase oocytes maturation rate but significantly increased blastocyst rate (58.06% vs. 48.19%)of parthenogenetic embryo.If FBS in maturation liquid of oocytes was replaced by ITS, the maturation rate, cleavage rate and blastocyst rate were basically unchanged.Adding ITS into embryo medium could increase blastocyst rate (68.30% vs. 56.82%)of parthenogenetic embryo of goat.If FBS in embryo medium was replaced by ITS,the cleavage rate didn’t change basically,while the blastocyst rate in ITS was obviously lower than that in FBS group(42.33% vs.56.82%).[Conclusion] ITS could promote maturation of oocyte in vitro and early embryonic development, in addition,ITS could replace serum in maturation medium of oocyte as serum-free culture system for conducting relevant researches.

Growth Differentiation Factor-9 Gene Expression of Mice Oocytes in Vitro and in Vivo

Mice preantral follicles were cultured in vitro for 12 days to achieve metaphase Ⅱ （M Ⅱ ） oocytes. Oocyte growth differentiation factor-9 （GDF-9） gene expression was measured during different growth stages to explore the relationship between oocyte maturation and GDF-9 gene expression. Preantral follicles of lO-day old mice were isolated from the ovaries and were cultured for 12 days. Oocytes from day 2 （D2）, D4, D6, D8, DIO, D12 cultured in vitro were named the in vitro group and oocytes of day 12 （D12）, D14, D16, D18, D20, D22 grown in vivo were named the in vivo group. Follicle survival, antrum formation and maturation rate were 89.5%, 51.8% and 56.6% respectively in follicles cultured in vitro. After RT-PCR and agarose gel electrophoresis, relative mRNA abundance of GDF-9 was measured in each group of oocytes. At day 8 - 12, the GDF-9 gene expression level of oocytes in vitro was significantly lower than that in vivo （P 〈 0.05）. We conclude that M Ⅱ oocytes can be obtained from in vitro culture of preantral follicles. The GDF- 9 gene expression of oocytes varies at different growth stages in vivo. The low expression of GDF-9 in oocytes cuhured in vitro may be the cause of their low developmental capacity.

Effects of in Vitro Maturation Time of Oocytes on Sheep Nuclear Transfer Efficiency

[Objective] The study aimed to provide references for the time of oocyte maturation in vitro and enucleation in the course of sheep nuclear transfer(NT).[Method] Compared the effects of different maturation time of oocytes on enucleation efficiency and reconstructed embryo development by means of blind enucleation and fluorescence microscopy.[Result] Treatment of IVM(in vitro maturation)19-21 h was significantly higher than IVM 16-18 h treatment in oocyte maturation rate(P<0.05)and was significantly higher than IVM 22-24 h treatment in enucleation rate(P<0.05).Three treatments had no significant difference in cleavage rate and blastocyst rate(P>0.05),but IVM 19-21 h treatment was significantly higher than the other 2 treatments in average cell number of blastocysts(P<0.05).[Conclusion] The appropriate in vitro maturation time of oocytes was 19-21 h for sheep nuclear transfer,which could significantly improve the quality of blastocysts according to the cell number per blastocyst(P<0.05).

Cloning of Rabbit Bone Morphogenetic Protein 15 and Its Expression During in vitro Maturation of Rabbit Oocytes

Partial cDNA sequence of rabbit BMP15 was cloned by RT-PCR from rabbit ovaries, showing a similarity of 83%-90% with the BMP15 nucleotide sequences in humans, mice, ovine, sheep, cows and pigs. The expression of BMP15 in rabbit cumulus-oocyte complexs during oocytes in vitro maturation （IVM） was measured by fluorescent quantitative RT-PCR method. BMP 15 was expressed at low levels in immature oocytes and increased to the highest level at 16h of IVM, which coincides with the time of cumulus cell expansion, then declined slowly under IVM cultivation. The expression pattern of BMP 15 suggested that it might be important in cumulus expansion in rabbits.

Optimizing Yanbian Cow Oocytes Mature in vitro and Cleavage System after Nuclear Transfer Based on Uniform Design

[Objective] The aim was to optimize Yanbian cow oocytes mature in vitro and cleavage system after nuclear transfer based on uniform design. [Method] Oocytes were recovered by aspiration method, and oocytes were matured in vitro （IVM） with different conditions, and then carried out nucleus transfer, fusion, activation and in vitro culture （IVC） of embryo. Effects of ovary storage temperature, maturation time and follicular diameter size on in vitro maturation and cleavage rates of cow oocytes were compared. [ Result] The best conditions of IVM of Yanbian cow oocytes was that： the oocytes of 8 mm diameter were matured in vitro for 24 hours when the ovaries were stored at 26℃ or 31 ℃. The best cleave conditions after nucleus transfer of oocytes was that： the oocytes of 6 mm or 8 mm diameter were cultured in vitro for 24 hours when the ovaries were stored at 26℃. [ Conclusion] The result has some reference to Yanbian cow and other cow breeding and population expanding propagation.

Nicotinamide mononucleotide supplementation improves the quality of porcine oocytes under heat stress

Background:Elevated ambient temperature-caused heat stress is a major concern for livestock production due to its negative impact on animal feed intake,growth,reproduction,and health.Particularly,the germ cells are extremely sensitive to the heat stress.However,the effective approach and strategy regarding how to protect mammalian oocytes from heat stress-induced defects have not been determined.Methods:Germinal vesicle(GV)porcine oocytes were cultured at 41.5℃ for 24 h to induce heat stress,and then cultured at 38.5℃ to the specific developmental stage for subsequent analysis.Nicotinamide mononucleotide(NMN)was dissolved in water to 1 mol/L for a stock solution and further diluted with the maturation medium to the final concentrations of 10μmol/L,20μmol/L,50μmol/L or 100μmol/L,respectively,during heat stress.Immunostaining and fluorescence intensity quantification were applied to assess the effects of heat stress and NMN supplementation on the key processes during the oocyte meiotic maturation.Results:Here,we report that NMN supplementation improves the quality of porcine oocytes under heat stress.Specifically,we found that heat stress resulted in oocyte maturation failure by disturbing the dynamics of meiotic organelles,including the cytoskeleton assembly,cortical granule distribution and mitochondrial function.In addition,heat stress induced the production of excessive reactive oxygen species(ROS)and DNA damage,leading to the occurrence of apoptosis in oocytes and subsequent embryonic development arrest.More importantly,we validated that supplementation of NMN during heat stress restored the meiotic defects during porcine oocyte maturation.Conclusions:Taken together,our study documents that NMN supplementation is an effective approach to improve the quality of oocytes under heat stress by promoting both nuclear and cytoplasmic maturation.

Role of ICSI in Non-male Factor Cycles as the Number of Oocytes Retrieved Decreases from Four to One

This study aimed to investigate whether intracytoplasmic sperm injection（ICSI） shows an advantage over in vitro fertilization（IVF） in non-male factor cycles as the number of oocytes retrieved decreases from four to one.We undertook a retrospective analysis of 1305 IVF/ICSI cycles of non-male factor in which four or fewer oocytes were retrieved.Comparisons were made between conventional IVF（CI） and ICSI when one,two,three or four oocyte（s） were retrieved.Primary outcomes including normal fertilization rate,proportion of embryos per obtained oocyte,cycle cancellation rate,implantation rate,clinical pregnancy rate（PR）,live birth rate（LBR）,cumulative PR and cumulative LBR were evaluated.The results showed that the normal fertilization rate（72.5% vs.50.0%） and the proportion of embryos per obtained oocyte（72.5% vs.55.0%） were significantly increased in one oocyte retrieved cycles in ICSI group as compared with CI group.However,the proportion of embryos per obtained oocyte was markedly decreased in ICSI group when three（52.3% vs.61.3%） or four（56.9% vs.64.0%） oocytes were retrieved.The implantation rates,clinical PRs,LBRs,cumulative PRs and cumulative LBRs in CI group were comparable to those in ICSI group when one,two,three or four oocyte（s） were retrieved.In conclusion,ICSI doesn＇t show advantages over IVF in low oocyte yield cycles of non-male factors,even when only one oocyte was retrieved.Key words

Manufacturing of SEM and TEM Samples for Oocyte

[ Objective] The research aimed to explore the manufacturing methods of scanning electron microscope （SEM） and transmission electron microscopy （TEM） for oocyte and provide technical support for related research. [ Method] Based on GV-and MII-stage oocytes, samples of SEM and TEM were prepared respectively, then ultrastructure changes were observed. [ Result] The results showed that the method needed few samples, keep intact cell morphology and can see clear ultrastructure. [Conclusion] The method is suitable for ultrastructural observation of oocyte.

Improvement of in vitro Cytoplasmic Maturation of Denuded Porcine Oocytes by Coculture with Follicular Mural Granulosa Cells

[Objective] This study aimed to improve the in vitro maturation quality of denuded porcine oocytes and provide scientific basis for establishing a stable and efficient denuded oocyte culture system. [Method] The first polar body extrusion rate, oocyte glutathione （GSH） content, positive rate of brilliant cresyl blue （BCB） staining and development potential of activated oocytes or fertilized oocytes were employed as main indicators to investigate the effects of follicular mural granulosa cell （MGC） coculture on cytoplasmic maturation of cumulus cell-removal oocytes （Denuded Oocyte, DO）. [Result] According to in vitro maturation results, compared with DO group, the first polar body extrusion rate of porcine oocytes in DO＋MGC group was not significantly different, but the nuclear maturation process was improved and was more similar to that in COC （cumulus-oocyte complex） group. Detection of GSH content in mature oocytes showed that there was no significant difference between DO＋ MGC group （optical density of 1 053.67） and COC group （optical density of 1 426.00） or between DO＋MGC group and COC＋GC group （optical density of 1 541.00）, however, GSH content in mature oocytes of DO group （optical density of 724.67） was significantly lower than that of COC group and COC＋GC group （P0.05）. Detection of glucose-6-phosphate dehydrogenase （G6PDH） activity showed that there was no significant difference in BCB positive oocyte rate between DO ＋MGC group （88.26% ） and COC group （92.75%） or between DO＋MGC group and DO group （82.86% ）, however, BCB positive oocyte rate of DO group was significantly lower than that of COC group （P0.05）. Furthermore, the cleavage rate and blastocyst rate of activated mature oocytes derived from DO ＋MGC group （94.98% and 43.67% , respectively） were significantly higher than those from DO group （52.54% and 8.97%, respectively） （P0.05）, and were not significantly different compared with those from COC group （97.11% and 38.30%, respectively）. In addition, the cleavage rate of fertilized oocytes derived from DO＋MGC group （72.65%） showed no significant difference compared with that from DO group （63.59%）, but the blastocyst rate of DO＋MGC group was significantly higher than that of DO group （9.88%） （P0.05）. [Conclusion] MGC coculture can significantly improve the in vitro cytoplasmic maturation quality of denuded porcine oocytes, thereby enhancing the subsequent developmental potential.

Application of PDE3 and Brilliant Cresyl Blue in In-vitro Culture of Sheep Oocyte

[Objective] The aim of this study was to increase the viability of sheep oocytes in vitro by using phosphodiesterase type 3（PDE 3） inhibitor milrinone combined with brilliant cresyl blue（BCB） staining.[Method] The differences between BCB tested and morphologically selected oocytes,as well as the effect of them on embryo development were compared;and then suitable inhibitive time of milrinone to sheep oocytes in vitro was studied and used in BCB-oocytes for in vitro embryo production（IVEP）.[Result] The BCB＋ oocytes percentage in A-and B-level sheep oocytes was 64.42%,which was extremely significantly higher than that in C-level（17.0%）.The maturing rate,cleavage rate and blastocyst rate of BCB＋ oocytes（86.16%,85.29% and 34.40%） of was significantly higher than those of BCB-oocytes（50.94%,36.19% and 6.73%）.The best time for PDE 3 inhibitor delaying the sheep oocyte mature in vitro was 6 h.In addition,the rate of embryo development in vitro could be significantly increased by inhibiting the BCB-oocytes for 6 h with Milrinone.[Conclusion] The study will provide reference for improving the efficiency of sheep oocytes culture in vitro.

In vitro Maturation of Tan Sheep Oocytes

[Objective] This study aimed to investigate the appropriate concentrations of follicle-stimulating hormone（FSH）, luteotropic hormone（LH） and estrodiol（E2） during in vitro maturation of Tan sheep oocytes. [Method] Tan sheep oocytes were divided into five groups for in vitro maturation culture： control group, FSH group（10,50, 100, 200 and 300 μg/ml FSH, respectively）, LH group（5, 10, 20, 50 and 100μg/ml LH, respectively）, E2group（5, 10, 25, 50 and 100 μg/ml E2, respectively）, and FSH ＋ LH group（100 μg/ml FSH ＋ 20 μg/ml LH）. The releasing rate of first polar bodies was analyzed. [Result] The maturation rate of Tan sheep oocytes in 100 μg/ml FSH ＋ 20 μg/ml LH group reached the highest（64.64%）, which was significantly higher than that in other four groups（P〈0.05）; among different FSH concentrations,100 μg/ml FSH was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）; among different LH concentrations, 20 μg/ml LH was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）; among different E2 concentrations, 50 μg/ml E2 was superior to other four concentrations and the control group, exhibiting significant differences（P〈0.05）. [Conclusion] Under the experimental conditions, 100 μg/ml FSH ＋20 μg/ml LH was the most appropriate hormone combination for in vitro maturation of Tan sheep oocytes.

Comparative Study on Activation and Fertilization of Mouse Oocytes at Different Ages

Comparisons of activation rates and fertilization rates were made among oocytes at different ages. Results showed that oocytes at different ages had different activation and fertilization rates when stimulated by sperm or ethanol. Oocytes at 15～24 h after the injection of hCG were readily activated by 8% ethanol. The activation rate of oocytes increased with the age of oocytes, up to the highest average of 81.6%, but decreased after 20 h posthCG. Oocytes at 20 h posthCG exhibited the highest immediate cleavage rate(48.0%) after being stimulated by ethanol. On the other hand, 13～15 h oocytes exhibited higher fertilization rates, and the older oocytes were more difficult to be fertilized by sperm in vitro. These suggest that oocytes can be activated in different ways; the mechanism of fertilization might be different from that of activation; and in vitro fertilization is more dependent on oocyte age.

Lethal（2）giant larvae is required in the follicle cells for formation of the initial AP asymmetry and the oocyte polarity during Drosophila oogenesis

The intricately regulated differentiation of the somatic follicle cell lineages into distinct subpopulations with specific functions plays an essential role in Drosophila egg development. At early oogenesis, induction of the stalk cells generates the first anteroposterior （AP） asymmetry in the egg chamber by inducing the posterior localization of the oocyte. Later, the properly specified posterior follicle cells signal to polarize the oocyte along the AP and dorsoventral （DV） axes at mid-oogenesis. Here, we show that lethal（2）giant larvae （lgl）, a Drosophila tumor suppressor gene, is required in the follicle cells for the differentiation of both stalk cells and posterior follicle cells. Loss-of-function mutations in lgl cause oocyte mispositioning in the younger one of the fused chambers, due to lack of the stalk. Removal oflgl function from the posterior follicle cells using the FLP/FRT system results in loss of the oocyte polarity that is elicited by the failure of those posterior cells to differentiate normally. Thus, we provide the first demonstration that lgl is implicated in the formation of the initial AP asymmetry and the patterning of the AP and DV axes in the oocyte by acting in the specification of a subset of somatic follicle cells.

Role of animal pole protuberance and microtubules during meiosis in sea cucumber Apostichopus japonicus oocytes

Fully grown oocytes of Apostichopus japonicus have a cytoplasmic protuberance where the oocyte attaches to the follicle. The protuberance and the oolamina located on the opposite side of the oocyte indicate the animal-vegetal axis. Two pre-meiotic centrosomes are anchored to the protuberance by microtubules between centrosomes and protuberance. After meiosis reinitiation induced by DTT solution, the germinal vesicle (GV) migrates towards the protuberance. The GV breaks down after it migrates to the oocyte membrane on the protuberance side. The protuberance then contracts back into the oocyte and the first polar body extrudes from the site of the former protuberance. The second polar body forms beneath the first. Thus the oocyte protuberance indicates the presumptive animal pole well before maturation of the oocyte.

First Babies from Cryopreserved Oocytes in Hungary

Objective To evaluate the value of oocyte cryopreservation （CP） in our clinical ICSI program. Methods Freezing procedure with medium containing 1.5 mol/L propanediol （PrOH） ＋ 0. 3 mol/L succrose and traditional slow-freezingprotocol were used. Thawed oocytes were fertilized with ICSI （4-6 h after thawing）, and fertilization was assessed 12-16 h later. Laser assisted hatching was performed on all transferred embryos and embryo transfer was carried out 48-72 h after ICSI. Results Eighty-five eggs were thawed and survival rate of 75.3% （64/85） was obtained. Sixty-four oocytes were inseminated with ICSI, 47fertilized （47/64; 73.4%） and a cleavage rate of 85% （40/47） was obtained. Embryo transfers were performed in 18 patients, and 4 （19%） resulted in clinical pregnancies. One of the pregnancies encountered first trimester abortion. Implantation rate were 17.2% （5/29） per embryo and 5.8% （5/85） per egg thawed. In all cases, chorion biopsy was performed resulting 46 XY kariotype. Conclusion Our results provide further evidence of that although egg freezing cannot currently claim to be a routine procedure in human IVF,, there will certainly be a place for oocyte CP in reproductive medicine in the future.

In vitro maturation of human oocytes maintaining good development potential for rescue intracytoplasmic sperm injection with fresh sperm

BACKGROUND The outcomes of the use of commercial in vitro maturation(IVM)medium to culture immature oocytes obtained from conventional ovulation induction,followed by rescue intracytoplasmic sperm injection(RICSI),are not ideal.It is thus difficult to widely adopt this approach in clinical practice.Therefore,it is necessary to explore methods for improving the clinical outcome of IVM.AIM To study the effect of sperm on the developmental potential of in vitro-matured oocytes in conventional culture.METHODS This was a retrospective study of patients whose immature oocytes were harvested from conventional oocyte stimulation cycles and underwent ICSI at our hospital between June 2018 and August 2020.RICSI was performed using sperm collected on the day of oocyte harvest(old)and sperm collected on the day of RICSI(fresh)and oocytes matured in vitro after 24 h of culture in conventional medium.The rates of in vitro oocyte maturation,normal fertilization,normal cleavage,day-3 top-quality embryos,and useful blastocyst formation were compared between the two groups.RESULTS In total,102 germinal vesicle(GV)-stage immature oocytes were cultured in the old sperm group.In the fresh sperm group,122 GV-stage immature oocytes were collected and cultured in vitro for 24 h.There were no significant differences in the general conditions of males and females between the two groups(P>0.05).The oocyte maturation,normal fertilization,and normal cleavage rates of the old and fresh groups were 51.0%vs 55.7%,61.5%vs 64.7%,and 93.8%vs 93.2%,respectively.None of the rates differed significantly(P>0.05)between the two groups.However,the day-3 top-quality embryo and useful blastocyst rates of the old and fresh sperm groups were 16.6%vs 63.4%;6.67%vs 34.6%,respectively.The day-3 top-quality embryos and useful blastocyst rates of the old sperm group were significantly lower than those of the fresh group(P<0.05).CONCLUSION In vitro maturation with conventional culture medium combined with the use of fresh sperm collected on the day of RICSI is an easy-to-implement strategy for patients whose oocytes are completely or mostly immature.

Oocyte vitrification:A local validation of the method

Is there a really need to validate oocyte vitrification technique in an ART laboratory before establishing it in daily practice? Validation of micromanipulationbased technique, in this case oocyte vitrification, is essential prior to enlarging its use to routine practice. Oocyte vitrification is a new worldwide used technique and legal recently inFrance. This micromanipulation needs to be performed by a skilled and experienced embryologist and requires an internal assessment in each ART unit before any wide use. We designed a prospective study, from September 2011 to July 2012, using sibling oocytes from women who recovered more than 12 Metaphase II oocytes. A part of freshly recovered oocytes underwent immediate ICSI while the remaining oocytes were vitrified. 87 couples undergoing ICSI were selected based on number of mature oocytes available on the recovery day after denudation. A part of fresh MII oocytes were microinjected and the others were vitrified using an open system (Cryotop?). The major criterion of interest was the number of embryo transferred/ number of Metaphase II ratio for after ICSI on fresh oocytes (42/211) versus vitrified/warmed oocytes (51/204) (p > 0.05). Secondary studied criteria were survival rate (80.5% ± 26.3%), fertilization rate (68.9 ± 33.5) and finally, cumulative pregnancy rate obtained in this study is 40.2%. One of the benefits of such practice is the limitation of embryo freezing. However, the study design delays oocytes warming cycles, due to pregnancies triggered by the transfer of fresh derived oocyte embryos and to the priority to transfer all the frozen embryos before starting oocytes warming. Moreover, no data is available about children’ health. Oocyte vitrification represents not only a change in our daily practice to improve cumulative pregnancy rate but also a promising tool to develop egg banking and donation. Clinical Trials Registration number: 209 R02.