The expression of ovulation related genes in CC is associated with patient and treatment characteristics, oocyte developmental potential and differs with the type of gonadotrophin used.

Multivariable models based on CC gene expression can be used to predict embryo development and pregnancy.

IVM of oocytes obtained ex vivo during the processing of ovarian cortex prior to cryopreservation is a procedure with emerging promise for patients at risk for fertility loss, as illustrated by the reported pregnancy. However, more data are needed in order to estimate the overall success rate and safety of this novel approach.

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STUDY QUESTION Can oocytes extracted from excised ovarian tissue and matured in vitro be a useful adjunct for urgent fertility preservation (FP)? SUMMARY ANSWER Ovarian tissue oocyte in-vitro maturation (OTO-IVM) in combination with ovarian tissue cryopreservation (OTC) is a valuable adjunct technique for FP. WHAT IS KNOWN ALREADY Despite the impressive progress in the field, options for FP for cancer patients are still limited and, depending on the technique, clinical outcome data are still scarce. STUDY DESIGN, SIZE, DURATION This was a retrospective cohort study conducted at a university hospital-affiliated fertility clinic between January 2012 and May 2019. PARTICIPANTS/MATERIALS, SETTING, METHODS The study included 77 patients who underwent unilateral oophorectomy for OTC. Cumulus-oocyte complexes (COCs) obtained during ovarian tissue processing were matured in vitro for 28–42 h. Oocytes reaching metaphase II stage were vitrified or inseminated for embryo vitrification. MAIN RESULTS AND THE ROLE OF CHANCE Overall, 1220 COCs were collected. The mean oocyte maturation rate was 39% ± 23% (SD). There were 64 patients who had vitrification of oocytes (6.7 ± 6.3 oocytes per patient). There were 13 patients who had ICSI of mature oocytes after IVM, with 2.0 ± 2.0 embryos vitrified per patient. Twelve patients have returned to the clinic with a desire for pregnancy. For seven of these, OTO-IVM material was thawed. Two patients had OTO-IVM oocytes warmed, with survival rates of 86% and 60%. After ICSI, six oocytes were fertilised in total, generating three good quality embryos for transfer, leading to a healthy live birth for one patient. In five patients, for whom a mean of 2.0 ± 0.8 (SD) embryos had been vitrified, seven embryos were warmed in total: one embryo did not survive the warming process; two tested genetically unsuitable for transfer; and four were transferred in separate cycles to three different patients, resulting in two healthy babies. In this small series, the live birth rate per patient after OTO-IVM, ICSI and embryo transfer was 43%. LIMITATIONS, REASONS FOR CAUTION The retrospective study design and the limited sample size should be considered when interpreting results. WIDER IMPLICATIONS OF THE FINDINGS The results of the study illustrate the added value of OTO-IVM in combination with OTC. We report the first live birth following the use of this appended technique combined with oocyte vitrification. STUDY FUNDING/COMPETING INTEREST(S) No external funding was used for this study. M.D.V. reports honoraria for lectures in the last 2 years from MSD and Ferring, outside the submitted work, as well as grant support from MSD. The other authors have nothing to declare. TRIAL REGISTRATION NUMBER N/A