Antral follicle count is a good marker of ovarian reserve. The number of antral follicles can vary each cycle and its count is very observer-dependent. For this reason, it should be assessed together with the measurement of anti-Müllerian hormone, which is a parameter with less variability.
Ovarian reserve, together with age, are the parameters that best predict the outcome of in vitro fertilization. When the ultrasound shows a normal to high number of antral follicles (more than 8), it can be expected that a good number of eggs will be obtained during ovarian stimulation and that the possibility of pregnancy will be greater. On the contrary, if only a few follicles are observed, the response will be lower and the possibility of pregnancy lower.