Factors associated with the collection of isolated immature oocytes during ovarian tissue cryopreservation.

Purpose: To identify patient characteristics associated with successful isolated immature oocyte retrieval (IsO) during ovarian tissue cryopreservation (OTC) and to determine whether they are predictive of the collection of larger numbers of oocytes.

Methods: We retrospectively analyzed all patients undergoing OTC with IsO for fertility preservation over three years of activity at a university hospital. Univariate and multivariate analyses were used to identify the patients with the highest and lowest chances of oocyte recovery, and those with the largest numbers of oocytes. We also analyzed the correlation of IsO with the number of ovarian fragments collected and histological parameters.

Results: We analyzed 257 consecutive patients undergoing these procedures, at a median age of 17.1 years [0.3-38.3 years]. Isolated oocytes were obtained from 47.1% of patients, and IsO was more likely in patients with ovulatory cycles (63.0% vs. 38.6%; P≤ .001), without chemotherapy before OTC (61.4% vs. 33.1; P< .001) and with non-malignant diseases other than Turner syndrome (77.5%). Oocyte collection failure rates were highest in patients with Turner syndrome (OR 25.0, 95% CI 3.99-157.0; P< .001) or undergoing chemotherapy with alkylating agents before OTC (OR 37.6, 95% CI 8.36-168.8; P< .001). Prepubescent status (P= .043) and large numbers of ovarian fragments (P< .001) were associated with the retrieval of larger numbers of oocytes. Oocyte recovery was correlated with the presence of follicles in the medulla, but not with follicular density.

Conclusion: The chances of IsO differ between patients. Identifying patients with the highest chances of success facilitates appropriate resource allocation.