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Updated: Nov 24, 2025
Fertility Preservation Through Oocyte Vitrification: Clinical and Laboratory Perspectives
Published on: September 16, 2021
Study of clinical experience with different approaches to controlled ovarian hyperstimulation: a focus on safety and
Svetoslav Stoev1, Ilko Getov2, Tanya Timeva3
1Medical University Sofia, Sofia, Bulgaria slavi1702@gmail.com.
Objectives:
Current retrospective cohort study analyses clinical database records of 4792 assisted reproduction procedures to assess the significance of target effectiveness endpoints from a safety perspective.
Methods:
Stimulation protocols with urinary, recombinant or combination of both types gonadotrophin preparations are compared according to the following primary endpoints: incidence of ovarian hyperstimulation syndrome (OHSS), cycle cancellation, follicle count, induced estradiol values, clinical pregnancy achieved and cycles reached embryo transfer/freezing. We have investigated the incidence of cases evaluated as 'risky for OHSS' by secondary efficacy endpoints (exogenous gonadotrophin exposure, luteinising hormone and progesterone values, oocyte yield, eggs with normal maturation). The following statistical methods were applied: descriptive statistics, Mann-Whitney U test, Kruskal-Wallis test, Pearson chi-square test, Fisher's exact test, binary logistic regression.
Results:
Only 16 cases (0.42%) of moderate and delayed OHSS were established. Three hundred and seven (8.6%) stimulation cycles have been cancelled, principally among urinary protocols. Although the clinical pregnancy rate does not differ significantly in compared groups, punctured follicle count, oocyte yield and progesterone level were higher for recombinant preparations, followed by combined and urinary protocols. Follicle count, mean estradiol and luteinising hormone levels are within the 'safe window' for all investigated groups, associated with minimised risk of stimulation cancellation. The mean follicle-stimulating hormone (FSH) dose was highest in urinary protocols at the same duration of stimulation compared with recombinant products. The younger age, bigger follicle count, oocytes yield, mature oocytes count, percentage of fertilised oocytes, more embryos transferred and the later day of embryo transfer are critical for both assisted reproduction techniques (ART) success rate and the safety profile of sterility treatment.
Conclusions:
Safety surveillance of ART exceeds the incidence of OHSS. Suboptimal effectiveness of stimulation protocols may also jeopardise the well-being of ART patients. Gonadotrophin exposure, induced values of sex hormones, and quantity and quality of extracted oocytes should be considered to minimise any unintended suffering of treated couples.
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