Complete Guide on Follicle Size for Egg Retrieval

Follicle size for egg retrieval is important for egg retrieval procedures, as larger, mature follicles typically indicate that the eggs are ready for retrieval and fertilization. Having multiple mature follicles can significantly increase your chances of retrieving viable eggs, leading to a successful pregnancy.

Monitoring follicle size helps fertility specialists determine the optimal time for egg retrieval, increasing the chances of successful fertilization and pregnancy.

In this guide, we'll explain into what follicles are, their importance in the IVF process and how the antral follicle count correlates with egg retrieval outcomes. With this guide, you’ll be one step closer to building the family of your dreams.

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What is the Ideal Follicle Size in Egg Retrieval?

The optimal follicle size for egg retrieval is about 18-22 mm in diameter when they are typically considered mature. Your fertility specialist will closely monitor your follicle size via ultrasound. When around 2-3 follicles are 17 to 18 mm in diameter, your fertility specialist may determine it’s time to administer the trigger shots.

The ideal number of follicles can vary, but generally, having around 15-30 mature follicles is considered optimal for egg retrieval. This balance maximizes the number of eggs retrieved while minimizing the risk of OHSS.

How Does Follicle Size for Egg Retrieval Impact Chances of Pregnancy?

The size of a follicle matters because it indicates the maturity of the egg inside. Larger follicles generally contain mature eggs, which are more likely to be successfully retrieved, fertilized, and develop into healthy embryos. Monitoring follicle size helps fertility specialists time the egg retrieval procedure accurately, ensuring that the eggs are at the optimal stage for fertilization. This precise timing increases the chances of a successful pregnancy.

Types of Follicles

• Primordial Follicles

  The most basic and immature stage of follicles, present from birth consisting of one oocyte surrounded by a single layer of granulosa cells. These follicles may remain dormant, receive stimulation to become antral then mature follicles, or eventually die.

• Antral Follicles

  Frequently referred to as “resting follicles”, these follicles are small measuring about two to nine millimeters. These follicles can be measured via ultrasound, and their number indicates that ovarian reserve is present. Antral follicles can become mature follicles leading to the release of an egg. 

• Mature Follicles

  These follicles are about 16-20 millimeters in diameter and are often large enough to ovulate. This means these follicles often rupture and release an egg in order to become the corpus luteum, which plays an important part in maintaining a pregnancy.

Antral Follicle Count vs. Eggs Retrieved

Antral Follicle Count (AFC) is a key indicator of a woman’s ovarian reserve. It is the number of antral follicles visible on an ultrasound at the beginning of a menstrual cycle. AFC provides insight into how many eggs a woman might be able to retrieve during an IVF cycle.

A higher AFC indicates a better ovarian reserve, which generally correlates with a higher number of eggs retrieved. However, it’s important to note that the quality of eggs also matters significantly for IVF success, and quality tends to decline with age.