Follicle Size

Definition - What does Follicle Size mean?

Follicle size is the diameter of ovarian follicles as measured by transvaginal ultrasound, typically reported in millimeters (mm). Follicle size is used along with hormone measurements to determine when follicles are mature and ready for egg retrieval as part of an in vitro fertilization (IVF) procedure. Measurements are interpreted in the context of the overall menstrual cycle because it is normal for follicles to grow throughout the cycle.

FertilitySmarts explains Follicle Size

Follicle size correlates with follicular maturity. Healthy immature follicles typically measure 2 to 5 mm in diameter. As estrogen levels climb, follicles mature and grow.

Individual IVF doctors may have different optimal follicle sizes that commonly range between 15 to 20 mm. Along with follicle size, serum estradiol level is taken into consideration. Once target size is achieved, gonadotropins also known as a trigger shot are used to stimulate ovulation.

Monitoring follicle size before ovarian stimulation and egg retrieval helps to optimize the quality and number of the eggs retrieved.

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