Follicle
A follicle is a small fluid-filled sac in the ovary that holds an egg. During IVF, medication encourages several follicles to grow so that multiple eggs can be collected.
A follicle is a small, fluid-filled sac in the ovary, each holding one immature egg.
Follicles in IVF
During ovarian stimulation, scans track how many follicles are growing and how large they are. When enough reach the right size, the eggs inside are collected at egg retrieval.
Sources and further reading
- ESHRE: Ovarian stimulation guideline (2025). Follicles during stimulation.
Source links checked on 7 September 2026. This source check is separate from medical review.
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