Health of 2-year-old children born after vitrified oocyte donation in comparison with peers born after fresh oocyte donation

Planned Oocyte Cryopreservation: A Review of Current Evidence on Outcomes, Safety and Risks

Although oocyte cryopreservation was initially used as a fertility preservation strategy for medical indications, it is now is increasingly used to circumvent age-related infertility. Outcomes following planned oocyte vitrification, also known as elective egg freezing, are limited. Current studies show higher success rates for individuals undergoing fertility preservation treatment under age 35. Additionally, while freezing 20 oocytes is optimal to achieve pregnancy, freezing at least 8-10 oocytes is recommended. While fertility is not guaranteed, current evidence demonstrates that planned oocyte vitrification is an overall safe, low risk method of fertility preservation to reduce the risk for age-related infertility.

Planned oocyte cryopreservation: the state of the ART

The objective of this review is to provide an update on planned oocyte cryopreservation. This fertility preservation method increases reproductive autonomy by allowing women to postpone childbearing whilst maintaining the option of having a biological child. Oocyte cryopreservation is no longer considered experimental, and its use has increased dramatically in recent years as more women delay childbearing for personal, professional and financial reasons. Despite increased usage, most patients who have undergone oocyte cryopreservation have not yet warmed their oocytes. Most women who cryopreserve oocytes wait years to use them, and many never use them. Studies have demonstrated that oocyte cryopreservation results in live birth rates comparable with IVF treatment using fresh oocytes, and does not pose additional safety risks to offspring. Based on current evidence, cryopreserving ≥20 mature oocytes at <38 years of age provides a 70% chance of one live birth. However, larger studies from a variety of geographic locations and centre types are needed to confirm these findings. Additional research is also needed to determine the recommended age for oocyte cryopreservation, recommended number of oocytes to cryopreserve, return and discard/non-use rates, cost-effectiveness, and how best to distribute accurate and up-to-date information to potential patients.

Effects of oocyte vitrification on gene expression in the liver and kidney tissues of adult offspring

Oocyte vitrification is an important assisted reproductive technology (ART) that preserves the fertility of unmarried patients with malignant tumors, and promotes the development of the oocyte donation program. In recent years, the effects of ART, including the vitrification of oocytes and embryos on the health of offspring, have attracted much attention; however, it is difficult to conduct long-term follow-up and biochemical evaluation in humans. In this study, we detected the effect of oocyte vitrification on gene expression in the organs of adult mice offspring by RNA sequencing for the first time. Our results showed that only a small amount of gene expression was significantly affected. Seven genes (Tpm3, Hspe1-rs1, Ntrk2, Cyp4a31, Asic5, Cyp4a14, Retsat) were abnormally expressed in the liver, and ten genes (Lbp, Hspe1-rs1, Prxl2b, Pfn3, Gm9008, Bglap3, Col8a1, Hmgcr, Ero1lb, Ifi44l) were abnormal in the kidney. Several genes were related to metabolism and disease occurrence in the liver or kidney. Besides, we paid special attention to the expression of known imprinted genes and DNA methylation-related genes in adult organs, which are susceptible to oocyte cryopreservation in the preimplantation stage. As a result, some of these transcripts were detected in adult organs, but they were not affected by oocyte vitrification. In conclusion, we first report that oocyte vitrification did not significantly change the global gene expression in offspring organs; nonetheless, it can still influence the transcription of a few functional genes. The potential adverse effects caused by oocyte vitrification need attention and further study.

The effects of vitrification on oocyte quality

Vitrification, is an ultra-rapid, manual cooling process that produces glass-like (ice crystal free) solidification. Water is prevented from forming intercellular and intracellular ice crystals during cooling as a result of oocyte dehydration and the use of highly concentrated cryoprotectant. Though oocytes can be cryopreserved without ice crystal formation through vitrification, it is still not clear whether the process of vitrification causes any negative impact (temperature change/chilling effect, osmotic stress, cryoprotectant toxicity, and/or phase transitions) on oocyte quality that translate to diminished embryo developmental potential or subsequent clinical outcomes. In this review, we attempt to assess the technique's potential effects and the consequence of these effects on outcomes.