Embryos go through several stages of development. The first stage, known as the germinal stage, comprises four distinct phases: fertilization, cleavage, blastulation, and implantation. Transferring an embryo before it reaches the blastocyst stage holds certain risks. Waiting until this stage offers several theoretical advantages.
After an egg is fertilized, it begins to divide into multiple cells. The large single-celled zygote begins to divide into smaller cells. During this phase, there is no increase in mass as the cells begin to multiply. Cell division occurs every 18 – 20 hours. Cell division may indicate a chromosomal or metabolic defect if it occurs too rapidly or too slowly. The embryo is transferred to the woman’s womb when the blastocyst phase is reached.
