Abstract
Study question
Are there any clinical or paraclinical predictive factors of Oocyte Post-warming Survival (OPS) rate?
Summary answer
Woman age, Body mass Index, estradiol level on triggering day and estradiol/oocyte ratio are critical predicting factors that should be considered before performing oocyte vitrification.
What is known already
Since the development and the validation of oocyte vitrification, we vitrify oocytes in different medical situations for patients who benefit ICSI. Although the OPS rate in our centre is satisfying, occasionally, it happens to be lower. OPS is dependent on quality of oocyte as demonstrated by the difference of OPS in oocyte donation/autologous cycles. The present study questions the existence of clinical and paraclinical factors predicting in OPS. In order to tackle this issue, we have assessed several parameters related to the woman and to her response to hormonal treatment known to influence oocyte quality in relation to OPS
Study design, size, duration
A retrospective observational study of 786 autologous oocyte vitrification cycles was performed from October 2011 to July 2018 in 5 situations: cycles where only a part of mature collected oocytes were vitrified [1] Partial oocyte vitrification program(n = 605), [2] Patients opposed to embryo cryopreservation(n = 2) and oocyte freeze-all cycles for the following reasons [3] Uncontrolled Ovarian hyperstimulation( = 89), [4] Unfavorable uterine environment/receptivity(n = 71) and [5] Absence of spermatozoa(n = 20). 1175 warming cycles were analyzed to identify predictive factors for OPS.
Participants/materials, setting, methods
Oocytes were vitrified/warmed using Kitazato media and system. The ratio of OPS survival was measured between the number of intact oocytes and the number of warmed oocytes. The factors assessed as potential predictors of OPS were: woman age, body mass Index (BMI), Estradiol level on triggering day (E2), E2/ number of recovered oocytes (EOR), number of recovered oocytes and maturity ratio (number of mature oocytes/number of recovered oocytes). Statistics were performed using SPSS software.
Main results and the role of chance
A total of 1175 studied warming cycles were performed and 5421 oocytes were warmed with a mean OPS rate of 84,6% (±22,6). OPS rates were comparable in all situations: [1] 3084/3688 (83,6%), [2] 6/6 (100%), [3] 931/1121 (83,1%), [4] 393/458 (85,8%), [5] 125/148 (84,5%). The mean woman age (33,2 years±4,9 vs 33,1 years ±4,3), mean woman BMI (23,1 kg/m2±3,9 vs 22,9 kg/m2±4,2), mean E2 (2587,7pg/ml±1140,5 vs 2513,2pg/ml±1098,7), mean EOR (207,5pg/ml±119,4 vs 196,0pg/ml ±119,4), mean number of total recovered oocytes (15,0±6,8 vs 14,7±6,8), mean maturity ratio (85,4%±13,7 vs 86,0%±14,2) showed no statistical difference in women with reduced OPS (≤85%) as compared to women with standard OPS (>85%). Subgroups analyses revealed significant higher occurrence of reduced OPS in advanced age women (>40years) (OR = 2,4; [95%CI:1,3-4,4] p < 0,05) as compared to women of other age categories: < 30years (OR = 0,5; [95%CI:0,2-0,9]), 30-35years (OR = 0,4; [95%CI:0,2-0,7]), 36-40years (OR = 0,2; [95%CI: 0,3-0,5]). The combination of advanced age with abnormal BMI ( < 18,5 or > 24,9kg/m2: OR = 7,3[95%CI:1,6-34,0] p < 0,01), or elevated E2 (>3000pg/ml: OR = 3,3[95%CI:1,0-11,0] p < 0,05) or atypical EOR ( < 140 or > 250pg/ml: OR = 3,7[1,1-12,2] p < 0,05) amplified the risk of reduced OPS. Women with abnormal BMI combined with elevated E2 (OR = 2,1[95%CI:1,1-3,9] p < 0,05) or atypical EOR (OR = 1,6[95%CI:1,0-2.6] p < 0,05) were also at higher risk of reduced OPS.
Limitations, reasons for caution
Oocyte vitrification is a manual technique that depends on the skill of the operator. Inter-operator variability was not taken into account in our statistical analyses neither were data regarding ovarian stimulation protocols nor were infertility etiologies.
Wider implications of the findings
This work enabled to identify patient or treatment related factors that highly influence the outcome of oocyte vitrification/warming cycles. Our findings will likely help refining criteria for the selection of candidate patients for oocyte vitrification or to cancel bad prognosis cycles.
Trial registration number
NA
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