Clinical Use of a Pronuclear Stage Score Following Intracytoplasmic Sperm Injection (ICSI) Compared with Chromosomal Status

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Objectives: Selection of viable embryos for transfer currently plays a significant role in the effort to increase in vitro fertilization (IVF) programs and embryos transfer pregnancy rates. Recently, studies have published new classification based for pronuclear (PN) stage. This score included the morphological appearance of pronuclei and nucleoli. Our purpose in this study was evaluated the role of PN morphology and compared embryo morphology preimplantation genetic diagnosis (PGD) from day + 3 embryos. Design: Retrospective study. Materials and Methods: A total of 21 cycles (74 embryos) from intracytoplasmic sperm injection (ICSI) procedure was evaluated in this study. For each embryo, the following data were recorded during sequential observations. PN morphology 16–20 hours after injection, embryo morphology about 68 hours after ICSI (day + 3) and PGD on day +3. Two patterns of pronuclear morphology were distinguished, according to position of the PN: aligned or close pronuclei and separated or unequal pronuclei. Nucleoli morphology was also performed based on: nucleoli aligned; nucleoli aligning and scattered nucleoli. Cumulative embryo score (CES) was performed in each embryo referring to PN and nucleoli morphology simultaneously. An embryo was classified as having good quality (GE) if more than 4 cells were present with less than 20% fragmentation at 68 hours after ICSI (day + 3). Probes with chromosomes X, Y, 18, 13 and 21 were numerically analyzed through the biopsy of 1 or two blastomeres. Results: The diagnosis was obtained in 70 embryos. Close or aligned PN showed to have a higher number of embryos with normal results to PGD when compared with embryos that had separated or unequal PN (56% vs. 45.5%, p<0.05). When nucleoli were aligned, best PGD results were noted when compared with aligning or scattered nucleoli (83.3%, 33.3% and 52.2% of normal embryos, respectively, p<0.05). Nucleoli aligning seemed to exhibit lower rates (33.3%) of numerical normality for these chromosomes when we compared with others embryos. Aligned PN and nucleoli provide a better score to the embryo with better PGD results for numerical normality (90.9%, p<0.05). CES and embryo morphology was also compared and 88% of GE demonstrated normal results to PGD. However, relationship between embryo morphology and PGD results was established only in embryos with aligned PN and nucleoli (88% GE vs. 12% no GE; p<0.005). Conclusions: Nucleoli and PN morphology can be a predictive factor to select embryos with normal chromosomal status and represents an efficient criteria for transfer citogenetically normal embryos in ICSI cycles.