Mature Follicle

Definition - What does Mature Follicle mean?

A mature follicle is a liquid-filled sac in the ovary that has grown to its maximum size and is set to burst and release the contained egg (i.e. is ready to ovulate).

A mature follicle is scientifically known as a Graafian follicle or an antral follicle.

FertilitySmarts explains Mature Follicle

A mature follicle develops under the influence of a hormone released from the pituitary gland called follicle-stimulating hormone (FSH) during the follicular phase of the menstrual cycle. It measures about 18 - 30 mm in a normal menstrual cycle.

In a normal cycle, only a single follicle matures while the rest degenerate. The mature follicle then produces estrogen, which functions to prepare the inner uterine lining to receive and implant a fertilized egg. The estrogen then suppresses the FSH production from the pituitary gland, which starts producing the luteinizing hormone in a burst, resulting in ovulation.

In a stimulated (medicated) cycle, several mature follicles are allowed to grow, to allow for the retrieval of more than one mature egg, The follicles contain fluid, in which the eggs float. To retrieve these eggs, the fluid is withdrawn by passing an ultrasound probe through the vagina to guide the passage of a fine needle into the ovarian follicles, which sucks the fluid out. The follicular fluid is then examined in an IVF laboratory to analyze the presence of eggs.

Another importance of a mature follicle is to predict a woman’s ovarian reserve (or the number of eggs available). This is done by counting the number of antral follicles (also known as the antral follicle count or AFC) in the ovary. The chances of a successful pregnancy are higher with an optimal AFC. In addition, the antral follicles produce the anti-Mullerian hormone (AMH), which is also used as an estimate of a woman’s ovarian reserve.

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