Embryo Assessment and Development

On a daily basis using a high powered microscope, the embryologist will assess the quality of the embyros by examining factors such as:

• cell division number
• timing of division
• cell size
• cellular components
• spatial arrangement, and
• degree of fragmentation, if any.

Poor quality embryos include those with improper cell division, high degree of fragmentation, or intracellular inclusions such as vacuoles. Assisted embryo hatching may be recommended if there is poor embryo quality or if the embryo shell (zona pellucida) is excessively thick. By the third day after retrieval, a healthy embryo should have approximately eight cells, and by the fifth day it is termed a blastocyst, which contains over 100 cells. Embryo transfer is normally done on day 3 after retrieval but blastocyst transfer on day 5 or 6 may be performed after discussion with the physician and embryologist.