Objective: To analyze the association between morphological details at different stages of culture with blastocyst development, with an aim to improve selection for transfer.
Design: Retrospective audit of data.
Setting: Tertiary referral center and university hospital.
Patient(s): Two hundred sixty-eight couples underwent 357 treatment cycles.
Intervention(s): Oocyte pickups for IVF or intracytoplasmic sperm injection (ICSI) after ovarian stimulation. Embryos were individually cultured and examined on days 0-2 for morphological details and developmental characteristics, and selected for transfer, freezing, or further culture.
Main outcome measures: The association of blastocyst development and pregnancy with morphological characteristics.
Result(s): Five morphological characteristics (appearance of the cytoplasm, pronuclei and nucleoli, cytoplasmic deficit, and developmental rate) showed the strongest association with blastocyst development. By combining information from all days of culture into a cumulative score, prediction was greatly improved, compared to only using day 2 morphology. Cytoplasmic dysmorphisms of the oocyte, including accumulation of smooth endoplasmic reticulum, were associated with poor developmental performance. Differential weighting of these characteristics was included in a new embryo scoring system, which showed a strong correlation with implantation.
Conclusion(s): Weighting individual morphological characteristics of zygotes and embryos and combining them into a cumulative embryo score can improve selection of embryos for transfer.