Mature Egg

Reviewed by Ashley Wong, MS, Clinical EmbryologistCheckmark | Last updated: April 16, 2020

What Does Mature Egg Mean?

An egg is mature after it has undergone two separate rounds of meiosis or cell division. These rounds of cell division reduce the number of chromosomes in the nucleus of the egg from 46 chromosomes to 23 chromosomes in preparation for fertilization by the sperm.

FertilitySmarts Explains Mature Egg

Just prior to ovulation, the developing egg must undergo two rounds of cell division in order to reduce the number of chromosomes in the nucleus from 46 chromosomes to 23 chromosomes. This process of chromosome reduction is known as egg maturation and creates a mature egg that is ready for ovulation and fertilization by sperm. When the 23 chromosomes in the nucleus of a mature egg combine with the 23 chromosomes in the nucleus of the sperm, the fertilized mature egg will again contain the 46 chromosomes necessary for healthy human development.

In women undergoing fertility treatments such as in vitro fertilization (IVF) or intrauterine insemination, and injection of human chorionic gonadotropin (hCG), also known as a trigger shot, is used to stimulate egg maturation in preparation for egg retrieval or ovulation. Due to various factors, not all eggs collected during egg retrieval will be mature eggs. Only mature eggs are eligible for the processes of fertilization and implantation.


Egg Maturation

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