This growing follicle can be seen by Transvaginal ultrasound daily- This is called follicular study. The study starts around 8th to 10th day of menstrual cycle and continues till the follicle ruptures. It usually ruptures after it achieves 20 mm size.

What is the maximum size of egg to rupture?

Ultrasound examinations

In the treatment group, the maximum mean follicle size, prior to rupture, was 30 ± 4.3 mm (range 20–50 mm).

At what size egg will release?

When your follicles have reached around 18-20mm in diameter they are deemed ready for egg collection. You'll be given a hormone trigger injection to stimulate your follicles to release the mature eggs that have been prepared in your follicles.