Oocyte maturation defect in women undergoing IVF: contributing factors and effects on mature sibling oocyte outcomes

This study aimed to identify demographic and clinical factors associated with low maturation rates and to investigate if the rate of immature oocytes impacts the outcomes of mature sibling oocytes.

Women undergoing their first IVF-ICSI cycle between 2018 and 2022 at a fertility clinic were included. Cycles were classified into five groups according to the proportion of Metaphase II stage oocytes (MII): Null (0% MII, n = 46), Poor (1-25% MII, n = 44), Low (26-50% MII, n = 453), Acceptable (51-75% MII, n = 1641), and Optimal (76-100% MII, n = 2642). Demographic characteristics and clinical outcomes were compared between the five groups. In patients with a Null/Poor maturation rate, subsequent cycle outcomes were also evaluated.

A total of 4826 cycles were included in the study; 69,909 oocytes were recovered, and 53,065 were MIIs (75.9%). The Null group was older, had lower levels of anti-Müllerian hormone (AMH), needed more gonadotropins and days of stimulation, had higher follicle stimulating hormone (FSH) levels on day 3, and had less follicles > 15 mm on the day of trigger. When the outcomes of mature oocytes were compared, fertilization, usable blastocyst, aneuploidy, and life birth rates were comparable among groups. A binary logistic regression model using number of oocytes, paternal age, and trigger type with live birth rate endpoint found no differences between the categories and the base line Poor category. When patients whose maturation rate was Null/Poor, 42 (47.0%) carried out a second cycle; the maturation rate increased (56.9 ± 31.5 vs. 11.6 ± 11.2%, P < 0.0001).

Our data suggest that poor responders are more likely to have low rates of oocyte maturation. The proportion of immature oocytes does not impact the outcomes of mature sibling oocytes. In patients with Null/Poor maturation in their first cycle, the subsequent cycle is often associated with improved maturation rates.