Abstract

Background: Extended embryo culture to the blastocyst stage remains a challenging strategy in in vitro fertilization (IVF), particularly in patients with a low number of mature oocytes (MII), even among young women. Objectives: The study evaluated blastocyst formation in young women with fewer than 5 MII oocytes undergoing IVF. It also analyzed factors associated with blastocyst formation in this patient group. Materials and methods: This retrospective study included 100 IVF cycles in patients aged < 35 years with < 5 MII oocytes. Cycles were stratified into two groups according to the number of MII oocytes (≤ 2 and 3 - 4 MII). Multivariate logistic regression analysis was performed to identify predictors of blastocyst formation. Results: The 3 - 4 MII group had a significantly higher rate of at least one blastocyst compared with the ≤ 2 MII group (86.8% vs. 65%; p = 0.014). However, no significant differences were observed in fertilization rate, blastocyst formation rate, or good-quality blastocyst rate between the two groups (p > 0.05). Multivariate analysis identified female age (OR = 0.68; p = 0.017) and number of MII oocytes (OR = 2.22; p = 0.013) as independent predictors of blastocyst formation, whereas AMH, BMI, and OSI were not statistically significant. Conclusion: The number of mature oocytes primarily influences the likelihood of achieving at least one blastocyst per cycle, whereas blastocyst quality appears to be independent of the number of MII oocytes.