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BACKGROUND A successful oocyte vitrification program is important for women with various indications for assisted reproduction technology. The objective of this study was to report the outcome of vitrification of oocytes, obtained through an oocyte donation program, by evaluating the embryo development, pregnancy and implantation rates (IRs) after blastocyst transfer. METHODS A total of 1098 oocytes were obtained from 78 donors. There were 312 oocytes used in the study group (vitrified oocytes) and 786 used in the control group (fresh oocytes). There were 34 recipients who received blastocysts obtained from vitrified oocytes and 58 recipients who received blastocysts from fresh oocytes. The fertilization rate, cleavage rate, embryo quality, pregnancy rate (PR) and IR were compared between groups. RESULTS Vitrified oocytes showed a survival rate of 89.4%. There was no difference in the fertilization rate (76.1 and 87.5%), Day 2 cleavage rate (96.3 and 98.0%) or blastocyst formation rate (41.3 and 45.3%) for the study and control groups, respectively. PRs, IRs and miscarriages rates (MRs) were similar for the study group compared with the control group (PR: 61.8 versus 60.0%; IR: 43.9 versus 42.9%; MR: 9.5 versus 5.9%). CONCLUSIONS The developmental competence of embryos obtained from vitrified oocytes is not affected by the vitrification procedure, since they preserve the potential to be fertilized and to develop into high-quality blastocysts, similar to embryos from fresh oocytes. The successful clinical outcome indicates the use of this procedure for oocyte donation programs and for oocyte storage in general.

Chromosome abnormalities are common in oocytes derived from patients undergoing IVF treatment. The proportion of oocytes displaying aneuploidy is closely related to maternal age and may exceed 60% in patients over 40 years old. However, little information currently exists concerning the incidence of such anomalies in oocytes derived from young fertile women. A total of 121 metaphase II oocytes and their corresponding first polar bodies (PB) were analysed with the use of a comprehensive cytogenetic method, comparative genomic hybridization (CGH). The oocytes were donated from 13 young women (average age 22 years) without any known fertility problems. All oocytes were mature at the time of retrieval and were unexposed to spermatozoa. A low aneuploidy rate (3%) was detected. These results clearly indicate that meiosis I segregation errors are not frequent in oocytes of young fertile women. The higher aneuploidy rates reported in embryos derived from donor oocytes could be due to aggressive hormonal stimulation, in combination with male factors. However a definite contributing factor remains to be elucidated. The data obtained during this study also illustrate that CGH accurately and efficiently detects aneuploidy, confirming that it is suitable for application in a clinical setting for the assessment of oocytes, via PB analysis.

Objective Evaluate sperm chromatin stability and its relationship with the rate of fertilization after procedures of intracytoplasmic sperm injection (ICSI) in a program of assisted reproduction. Design Prospective study. Setting Institute of Gynecology and Reproduction. Patients Thirty-three women with their respective partners (12 couples in the study group and 21 couples in the control group) participating in a program of assisted reproduction. The study group was defined as men with >30% of nondecondensed spermatozoa (high sperm chromatin stability). Interventions A part of each seminal sample was used to evaluate sperm chromatin stability under SDS and EDTA treatment and the second aliquot was used for the ICSI procedure. Fertilization was evaluated 16-18 h post sperm injection at a pronuclear stage. The fertilized oocytes were further cultured for 24-48 h before transfer to the patient. Main outcome measures Fertilization rate.Results Thirty-five oocytes (35.7%) in the group of study and 109 oocytes (78.9%) in the control group showed two pronuclei (P<0.001). The coefficient of determination between the SDS+EDTA (Grade 2) and rate of fertilization was r 2 =0.85 (P<0.001) and the coefficient of regression was 1.72±0.19 (β±ES) (P<0.001). Conclusions High sperm chromatin stability is a factor which reduces the rate of fertilization after ICSI procedure.

The aim of the present study was to determine the impact of oxygen concentration on implantation, pregnancy and delivery rates in IVF patients older than 40 year old with transfer of blastocysts. Included were 558 women aged 23-45 years old undergoing IVF/ICSI procedures whose embryos were cultured at blastocyst stage under two different oxygen environments (a bi-gas system: 5.6% CO2 in air and a tri-gas system: 5.6% CO2, 5% de O2 and 89.4% N2). The main outcome measures of this study are implantation, pregnancy and delivery rates. Implantation, pregnancy and delivery rates are found to be reduced in women older than 40 years old. The implantation and pregnancy rates are significantly higher in women older than 40 years old from the 5% of O2 group, in comparison to the 20% group (25.00% versus 2.70% and 41.38% versus 5.56%; P < 0.05). The deliveries rates were 13.79% and 5.56% in the 5% and 20% oxygen groups respectively (P: NS). The birthweight was similar in both study groups (P: NS). Gestational age was significantly longer in wo- men from the 5% of O2 group, in comparison to the 20% (36.87 versus 35.87 weeks, P < 0.05). Results indicated that the embryonic culture with 5% of oxygen and transfer of blastocysts in women older than 40 years old improve the results in the in Vitro fertilization/intracytoplasmic injection procedures (IVF/ICSI)