Antral follicle count is one way to predict ovarian reserve.
Chronological age and ovarian reserve are generally parallel. However, this can vary enormously. The number of follicles, each containing one egg, which are available in the ovarian “pool” or reserve relates to the chance of success of in vitro fertilization (IVF). These numbers decline with age, and in some women decline abnormally fast. Methods of predicting the potential outcome of IVF can be important in making medical decisions for couples trying to conceive.
One important tool for measuring the ovarian reserve is a direct measure of the follicles as they emerge in a given month, called the antral follicle count. The number of small follicles in the ovary during a menstrual period are observed using ultrasound. At this point, there are no large follicles and the pool of follicles, which will emerge that month, are beginning to grow. As the fluid accumulates, even a few milliliters (a teaspoon equals 5ml) of fluid in the antral follicle can produce a measurable echo on the highly sensitive ultrasound machines used for transvaginal evaluation of the ovaries. Follicles between 2 and 5mm can be visualized and counted.
The antral follicle count must be done when the follicles have not begun to grow. Thus it is scheduled on day two, three or four of the cycle prior to considering IUI or IVF therapy. This test can give a good idea of the ovarian reserve and this relates to prognosis for the future for IVF since there is not a huge variation from month-to-month. If the total number of antral follicles is under 5, most patients turn out to be low responders in IVF treatment. They also have very low spontaneous pregnancy rates.
There are other ways to measure ovarian reserve besides the antral follicle count, such as the AMH test.
For more information, click here for a Fact Sheet about ovarian reserve.