Immature Egg

What Does Immature Egg Mean?

An immature egg has not undergone the necessary cell division to reduce the number of chromosomes in the nucleus of the egg from 46 chromosomes to 23 chromosomes.

Immature eggs cannot be fertilized by sperm and will not produce a viable embryo. Fertility is affected when eggs do not mature.

FertilitySmarts Explains Immature Egg

In order to produce and mature a viable egg during ovulation, ovarian follicles must undergo a cell division process called meiosis, which is a process of cell division that is specific to eggs and sperm. Meiosis reduces the number of chromosomes in the nucleus of the egg from 46 chromosomes to 23 chromosomes which allows for fertilization by the sperm.

Follicle Size

Smaller than average follicles found within the ovary may not mature readily and may be more likely to produce immature eggs. An immature egg is not capable of being fertilized by the sperm as the nucleus contains too many chromosomes.


During in vitro fertilization (IVF), the process of egg maturation may be stimulated with an injection of hormone human chorionic gonadotropin (hCG), or a trigger shot. During an egg retrieval procedure, it is common for some immature eggs to be collected in addition to mature eggs because all follicles are aspirated. Stimulation protocols can be adjusted to improve the rate of mature eggs retrieved if a high percentage of eggs are found to be immature.


It may be possible to take immature eggs collected during the egg retrieval process and mature them in the lab through in vitro maturation (IVM). These lab-matured eggs can then be fertilized by the sperm to produce an embryo. This is considered to be an alternative treatment that remains a controversial aspect of assisted reproductive technology (ART).


Immature Oocyte

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