Early cleavage of human embryos to the two-cell stage after intracytoplasmic sperm injection as an indicator of embryo viability

TLDR

IVF embryos are selected for transfer based on morphology and development rate, but when many embryos appear similar, choosing the best one is often left to chance. The authors propose a simple, novel method that pre‑selects embryos cleaving early to the two‑cell stage to improve selection. They applied this method to ICSI embryos, defining early cleavage as reaching the two‑cell stage by 27 h post‑injection and transferring such embryos when available. Early cleavage occurred in 61.4 % of cycles and was associated with a significantly higher clinical pregnancy rate (25.9 % vs.

Abstract

In-vitro fertilization (IVF) embryos are selected for transfer on the basis of morphology and rate of development. However, when a number of embryos have similar characteristics, the selection of the best embryos is left to chance. Recently, we proposed a simple, novel method to overcome this problem, based on pre-selection of embryos cleaving early to the two-cell stage. In this study we have adopted the same method to choose embryos fertilized after intracytoplasmic sperm injection (ICSI). Fertilized embryos that had cleaved to the two-cell stage by 27 h post-injection were designated as 'early cleavage' embryos, while those that had not yet reached the two-cell stage were designated as 'no early cleavage'. In all cases, the early cleavage embryos were transferred when available. Early cleavage was observed in 54 (61.4%) of the 88 cycles assessed. There were significantly (P = 0.04) more clinical pregnancies in the early cleavage group, 14/54 (25.9%), compared with the no early cleavage group 2/34 (3.2%). No differences between the groups were found when comparing key parameters (age, stimulation protocol and semen characteristics) of the couples. Using the ICSI technique, we have shown that early cleavage to the two-cell stage is not influenced by the timing of fertilization, and is more likely due to intrinsic factors within the oocyte or embryo that promote embryo cleavage after fertilization.