Embryo Grading

Diagnostic Tests Females
January 19, 2018

Egg Retrieval and Insemination Day 0
Egg maturity is important because a mature egg has the best chance of being fertilized. There are three different stages of egg maturation:
Germinal vesicle (GV): The egg has not begun meiosis yet, so it is considered immature.
Metaphase I (MI): The egg is in the first phase of meiosis; however, it is still not completely mature because it has not entered the second phase of meiosis. This kind of immature egg may mature after a couple of hours of temperature-controlled incubation.
Metaphase II (MII): The egg is in the second phase of meiosis and is mature. Eggs at this stage of maturity are ready for fertilization.
Clear cytoplasm/normal shape
Single distinct polar body
Clear/thin zona pellucida
Slightly grainy cytoplasm/misshapen
Fragmented/abnormal polar body
Slightly pigmented/amorphous zona
Cytoplasmic bodies
PV debris
Dark/grainy cytoplasm/misshapen
>1 polar body structure
Pigmented/thickened zona
PV debris
Fertilization Check Day One
Fertilization can be seen 16 to 22 hours post insemination. Normal fertilization is identified by exactly two pronuclei in the center of the single cell zygote. Fertilization is considered abnormal when there is only one pronucleus or when there are more than two pronuclei.

Multicell Grading Day Two/Three

On day two the single cell zygote should divide into an embryo (approx. two to four cells). On day three the embryo should continue to divide (four to eight cells).

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