Dominant follicle

A dominant follicle is the single largest follicle that emerges during a natural menstrual cycle and continues to grow while other follicles in that cycle stop developing. It typically reaches around 18–24mm before ovulation, when it releases a mature egg. On ultrasound, tracking the growth of the dominant follicle helps predict the timing of ovulation, which is useful for planning timed intercourse, IUI, or deciding when to trigger ovulation. In stimulated IVF cycles, multiple follicles are encouraged to grow together rather than allowing one to dominate.

Also known as: lead follicle, leading follicle

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.