Table 2 The basic clinical and technical requirements for assessment of the AFC in clinical practice (reproduced with permission from Broekmans et al.

Clinical considerations

Technical considerations

   Select patients with regular menstrual cycles with no co-existing pathological condition that could technically affect the counting of follicles, such as ovarian endometriosis or previous ovarian surgery

A limited number of personnel, appropriately trained in transvaginal sonography should perform AFCs in each unit

Real-time, two-dimensional imaging is adequate

Count follicles between days 2 and 4 of a spontaneous menstrual or oral contraceptive cycle to avoid the effect of intra-cycle variation

Include all antral follicles of 2-10 mm in diameter

Use a transvaginal transducer

Use a probe with a minimum frequency of 7 MHz, which is maintained in an adequate condition and able to resolve a structure of 2 mm in diameter

   Use a systematic process for counting antral follicles:

1. Identify the ovary

2. Explore the dimensions in two planes (perform a scout sweep)Decide on the direction of the sweep to measure and count follicles

3. Measure the largest follicle in two dimensions

A. If the largest follicle is ≤10 mm in diameter:

i. Start to count from outer ovarian margin of the sweep to the opposite margin

ii. Consider every round or oval transonic structure within the ovarian margins to be a follicle

iii. Repeat the procedure with the contralateral ovary

iv. Combine the number of follicles in each ovary to obtain the AFC

B. If the largest follicle is > 10 mm in diameter:

i. Further ascertain the size range of the follicles by measuring each sequentially smaller follicle, in turn, until a follicle with a diameter of ≤10 mm is found

ii. Perform a total count (as described) regardless of follicle diameter

iii. Subtract the number of follicles of > 10 mm from the total follicle count