Fig. 2

Transvaginal ultrasound images during three follicle wall biopsy (FWB) procedures. a–d ovary with a small follicle size; e–h ovary with a medium follicle size; i–l ovary with a large follicle size; a, e, and i follicles ready to be biopsied; b, f, and j the 12 G needle/ cannula can be seen within the ovary but outside the follicle; c, g, and k the cannula and the biopsy forceps advance into the follicle antrum; d, h, and l biopsy forceps in close contact with the follicle wall to harvest the FWB tissue; m-q diagram illustrates steps of the FWB procedure; m cannula outside the ovary; n cannula inside the follicle antrum showing the extended tip of the biopsy forceps closed; o biopsy forceps opened inside the follicle; p biopsy forceps harvesting the FWB sample and bulging inside the follicle wall; q biopsy forceps being retrieved closed toward the cannula; a mark in the follicle wall can be seen sometimes immediately after pulling back the biopsy forceps. Simultaneously after the retrieval of the biopsy forceps from the cannula, a clean sample of follicular fluid is obtained immediately. n, needle, f, forceps; ft., forceps tip