Oocyte cryopreservation - current scenario and future perspectives: A narrative review

Abstract

Oocyte cryopreservation is a boon for women undergoing assisted reproductive technology. With the evolution in the technique of cryopreservation over the last three decades, there has been an exponential rise in the number of oocyte cryopreservation cycles for diverse indications. Apart from cancer patients, it has also been promoted as a mode of fertility insurance to overcome the age-related decline in fertility as well as post-surgical decline following endometriosis surgery. The objective of the review is to evaluate its clinical applications, ideal age at freezing, optimal oocyte number, freezing method of choice, efficacy, safety and recent advances. In the last decade, vitrification has surpassed slow freezing for oocyte cryopreservation. Although closed system of vitrification provides the aseptic environment, open vitrification is commonly followed in practice. Early to mid-thirties is a reasonable age group for planned oocyte cryopreservation, although it might be recommended at a younger age, in patients with diminished ovarian reserve. The patients should be motivated to preserve around 14–20 mature oocytes for successful live birth. Various studies have shown comparable fertilisation and pregnancy rates between Intracytoplasmic sperm injection with fresh and frozen-thawed oocytes. The available evidence has shown no increase in the incidence of congenital abnormalities in babies born through vitrified oocytes. In the future, image analysis using artificial intelligence, and spindle visualisation using poloscope may further enhance the outcome of oocyte cryopreservation.

State of the art in assisted reproductive technologies for patients with advanced maternal age

“…Recent publications reported that survival rate after cryopreservation was increased recent years, which confirms the influence of methodological approaches to female gamete cryopreservation provided by optimal ART (Pai et al, 2021). The turning point in the improvement of oocyte cryopreservation methods was the use of vitrification (Kuleshova et al, 1999).…”

A comprehensive review and update on human fertility cryopreservation methods and tools

“…Medical reasons include mainly sickle cell anemia, severe endometriosis, diminished ovarian reserve, autoimmune diseases, and ovarian insufficiency risk due to genetic conditions such as the Fragile X premutation, and Turner syndrome ( 4 ). Other reasons are the X chromosome deletion and patients that have undergone gender diversity as transgender with affected fertility status ( 5 ). Practically, all the concerns regarding embryo cryopreservation, such as ethical, legal, and religious can be challenged by the oocyte cryobanking choice.…”

“…For instance, at first, FP in patients undergoing gonadotoxic treatments is either the retrieval of oocytes (preferably mature) and spermatozoa from ejaculation or surgically recovered before cancer therapy treatment, or alternatively, the cryopreservation of embryos after an IVF cycle, as reported in the guidelines applied recently ( 3 , 220 ). In addition, oocyte cryopreservation has been extensively used and recommended for social freezing reasons, today referred to as “planned oocyte cryopreservation”, and for the establishment of donor egg banks ( 5 , 220 , 221 ).…”

Lipid modification to improve cryotolerance of gametes, embryos and larvae and its potential application in aquaculture species: a review

“…On the other hand, the embryo contain genetic material from both maternal and paternal sides. Compared to sperm, the larger size of oocytes and embryos reduces their cryotolerance (Pai et al, 2021). As oocytes and embryos share similarities in freezing sensitivity, the methods to modify their lipid compositions are discussed together.…”