First meiosis errors in immature oocytes generated by stimulated cycles

Objective: To investigate chromosomal errors detected by first polar body (PB) biopsy in relation to the nuclear maturity of the oocytes. Design: Retrospective study. Setting: Reproductive medicine unit. Patient(s): Eighty-seven cycles were examined by PB biopsy for aneuploidy. Indications were maternal age >= 38 years (49 cycles), repeated IVF failures (22 cycles), and others (16 cycles). Intervention(s): First polar bodies were analyzed for the chromosomes 13, 16, 18, 21, and 22 in both in vivo and in vitro matured oocytes. Euploid oocytes were inseminated by intracytoplasmic sperm injection. Main Outcome Measure(s): Chromosomal status of the analysed oocytes, development after intracytoplasmic sperm injection, pregnancy, and implantation rights. Result(s): In in vitro matured oocytes, the proportion of chromosomal abnormalities was higher than in vivo matured oocytes (70% vs. 54%, P <.005), with complex abnormalities being the prevailing defect (62% vs. 40%, P <.001). Conversely, the presence of an extra chromatid or the lack of a chromatid was more frequent in in vivo than in in vitro matured oocytes (55% vs. 34%, P <.001) Conclusion(s): The low viability of in vitro matured oocytes from stimulated cycles could be relaxed to a significantly higher proportion of chromosomal abnormalities compared with in vivo matured oocytes. Complex abnormalities involving two or more chromosomes, gave the strongest contribution to the detected increase.