In vitro maturation and the development to the blastocyst stage of immature oocytes collected from IVM/F-cycles

Abstract

Objective: This study was performed to examine the maturation and the development to the blastocyst stage of immature oocytes collected from the cycles to which blastocyst stage embryos were transferred.Design: Cumulus-oocyte complexes (COCs) were collected following only HCG-priming for IVF-ET cycles with high risk of OHSS. At the time of oocyte collection, COCs were classified into three groups in accordance with their appearances: group I, oocytes with dispersed cumulus cells; group II, oocytes with compacted cumulus cells; and group III, oocytes with sparse cumulus cells. The in vitro maturation and blastocyst rates were compared among these groups.Materials/Methods: From November 2001 to March 2002, 293 of IVM/F-ET were performed. Of them, 61 cycles of 51 patients (mean age: 32.3 ± 4.1 years) were transferred the blastocyst stage embryos. These patients had experience of OHSS and thus were primed with 10,000 IU HCG 36 hours before oocyte collection. Oocytes were aspirated between cycle day-7 and -18. The normal COCs were divided into three groups according to their appearance. The immature oocytes were cultured in maturation medium, YS containing 30% (v/v) hFF, 1 IU/ml FSH, 10 IU/ml HCG and 10 ng/ml rhEGF. Fertilization was induced by ICSI. All zygotes were cocultured with cumulus cells in 10 ml YS medium containing 10% hFF until day 7 after oocyte collection. Blastocyst transfers were performed on cycle day 5.Results: The mean number of oocytes collected in IVM/F-blastocyst transfer cycles was 25.9 ± 9.9. Of 1578 COCs, those assigned to group I, II and III were 39.4% (622/1578), 32.9% (519/1578) and 27.7% (437/1578), respectively. The total maturation rate (93.3%, 580/622) in group I was significantly higher than those of group II (64.0%, 332/519) and group III (73.0%, 319/437) (P <0.01). Especially, 35% of COCs in group I (218/622) was matured on the day of oocyte aspiration. The rates of fertilization and cleavage were similar among three groups. The development rate to the blastocyst stage in group I (64.0%, 307/480) was also significantly higher than those in group II (39.6%, 103/260) and group III (46.6%, 116/249) (P <0.01). Thirty-three cycles (54.1%) became clinically pregnant and in 28 cycles (45.9%) pregnancies are ongoing. Implantation rate in the present study was 26.2%.Conclusions: These results suggest that there should be a positive correlation between appearances of COCs and embryonic developmental competence in IVM/F-blastocyst transfer cycles.Supported by: Maria Infertility Hospital. Objective: This study was performed to examine the maturation and the development to the blastocyst stage of immature oocytes collected from the cycles to which blastocyst stage embryos were transferred. Design: Cumulus-oocyte complexes (COCs) were collected following only HCG-priming for IVF-ET cycles with high risk of OHSS. At the time of oocyte collection, COCs were classified into three groups in accordance with their appearances: group I, oocytes with dispersed cumulus cells; group II, oocytes with compacted cumulus cells; and group III, oocytes with sparse cumulus cells. The in vitro maturation and blastocyst rates were compared among these groups. Materials/Methods: From November 2001 to March 2002, 293 of IVM/F-ET were performed. Of them, 61 cycles of 51 patients (mean age: 32.3 ± 4.1 years) were transferred the blastocyst stage embryos. These patients had experience of OHSS and thus were primed with 10,000 IU HCG 36 hours before oocyte collection. Oocytes were aspirated between cycle day-7 and -18. The normal COCs were divided into three groups according to their appearance. The immature oocytes were cultured in maturation medium, YS containing 30% (v/v) hFF, 1 IU/ml FSH, 10 IU/ml HCG and 10 ng/ml rhEGF. Fertilization was induced by ICSI. All zygotes were cocultured with cumulus cells in 10 ml YS medium containing 10% hFF until day 7 after oocyte collection. Blastocyst transfers were performed on cycle day 5. Results: The mean number of oocytes collected in IVM/F-blastocyst transfer cycles was 25.9 ± 9.9. Of 1578 COCs, those assigned to group I, II and III were 39.4% (622/1578), 32.9% (519/1578) and 27.7% (437/1578), respectively. The total maturation rate (93.3%, 580/622) in group I was significantly higher than those of group II (64.0%, 332/519) and group III (73.0%, 319/437) (P <0.01). Especially, 35% of COCs in group I (218/622) was matured on the day of oocyte aspiration. The rates of fertilization and cleavage were similar among three groups. The development rate to the blastocyst stage in group I (64.0%, 307/480) was also significantly higher than those in group II (39.6%, 103/260) and group III (46.6%, 116/249) (P <0.01). Thirty-three cycles (54.1%) became clinically pregnant and in 28 cycles (45.9%) pregnancies are ongoing. Implantation rate in the present study was 26.2%. Conclusions: These results suggest that there should be a positive correlation between appearances of COCs and embryonic developmental competence in IVM/F-blastocyst transfer cycles. Supported by: Maria Infertility Hospital.