Embryos with morphokinetic abnormalities may develop into euploid blastocysts.

Irregular cleavage divisions are expected to produce chromosomally deviant embryos. We investigated whether embryos from irregular cleavages could develop into euploid blastocysts, and, if so, whether any evidence existed of a self-correction mechanism of the embryo. We also investigated the role of different dynamic aspects of morula compaction in this process. A total of 791 embryos from 141 patients undergoing pre-implantation genetic screening were retrospectively analysed using a time-lapse imaging system, and multiple cell divisions were evaluated. A total of 276 embryos developed into blastocysts suitable for biopsy and chromosome screening through array-comparative genomic hybridization. As well as testing trophectoderm biopsy specimens for aneuploidy, excluded cells of 18 blastocysts, which developed from partially compacted morulas, were also analysed. Unique data on the developmental fate of embryos with cleavage abnormalities are presented, and a potential mechanism of 'aneuploidy rescue' is postulated through which mosaic embryos may form partially compacted morulas to exclude aneuploid cells. In addition, this process seems to be less efficient in older women. The data obtained also provide further evidence that excluded cells should not be used to infer the cytogenetic status of the embryo.

Freezing spermatozoa obtained by testicular fine needle aspiration: a new technique.

Testicular fine needle aspiration (TEFNA) of spermatozoa in azoospermic patients in advance of intracytoplasmic sperm injection could be useful to avoid the possibility of no recovery of spermatozoa on the day of oocyte retrieval. The conventional freezing procedure for these spermatozoa is not appropriate because of their very low number and poor in-situ motility. This article presents a new procedure for the freezing of TEFNA-recovered spermatozoa. A total of 1063 spermatozoa (10-340 cells/sample) were frozen by this method for research purposes. Before freezing, 13.7% were motile. The recovery rate after thawing was 100%. After thawing, 3.6% motility was observed. In a separate study group, the total number of frozen spermatozoa was 431 (2-300 cells/sample). Before freezing, the sperm motility rate was 3.5%. After thawing, 100% of the spermatozoa were retrieved with a motility rate of 2.3%. One biochemical pregnancy was obtained. The procedure yielded excellent recovery and good motility rates after thawing. However, because of the low number of cases, any conclusion about the efficiency of the technique is premature.

Evidence-based clinical outcome of oocyte slow cooling.

In the last few years, there has been a significant improvement in oocyte cryopreservation techniques. To investigate the clinical significance of oocyte freezing, an assessment of the cumulative pregnancy rate per started cycle derived from the use of fresh and frozen-thawed oocytes was performed. Between 2004 and 2006, 749 cycles were carried out, in which no more than three fresh oocytes were inseminated either by standard IVF or microinjection. Supernumerary mature oocytes were cryopreserved by slow cooling. Cryopreservation of fresh embryos was performed in rare cases to prevent the risk of ovarian hyperstimulation syndrome using a standard embryo freezing protocol. Fresh embryo transfer cycles totalled 680, 257 of which resulted in pregnancy. The pregnancy rates per patient and per transfer were 34.3% and 37.8% respectively. When frozen-thawed oocytes were used, following 660 thawing cycles, 590 embryo transfers were performed in 510 patients. Eighty-eight pregnancies were achieved with embryos from frozen oocytes, with a success rate of 17.2% per cycle. When fresh and frozen-thawed cycles were combined, the number of pregnancies was 355, giving a cumulative pregnancy rate of 47.4%. Oocyte cryopreservation can contribute considerably to the overall clinical success, ensuring a cumulative rate approaching that achievable with embryo storage.

Differential sucrose concentration during dehydration (0.2 mol/l) and rehydration (0.3 mol/l) increases the implantation rate of frozen human oocytes.

Novel protocols have increased survival and fertilization rates of cryopreserved oocytes. Nevertheless, in most cases clinical experiences have been disappointing or contradictory. Human oocytes of 141 patients were cryopreserved using a modified slow-cooling protocol involving 1.5 mol/l propane-1,2-diol (PrOH) and 0.2 mol/l sucrose during dehydration, while rehydration was conducted applying decreasing concentrations of PrOH and 0.3 mol/l sucrose. One thousand and eighty-three oocytes were frozen and 403 were thawed, with a survival rate of 75.9%. Among the 306 surviving oocytes, 252 were microinjected and 192 (76.2%) showed two pronuclei. One hundred and eighty zygotes (93.8%) cleaved. The proportion of good quality embryos (grade I and II) was 86.2%. All embryos were transferred and 17 clinical pregnancies were obtained. Pregnancy rates were 21.3% per transfer, 21.8% per patient, and 18.9% per thawing cycle. The implantation rate was 13.5% while the miscarriage rate was 11.8%. To date, four babies have been delivered, while the remaining pregnancies are ongoing. Increased oocyte survival rates can be achieved by moderately high sucrose concentrations in the freezing and thawing solutions. This also ensures elevated success rates in terms of fertilization, embryo development and clinical outcome.