Abnormality of the genital system Empty ovarian follicle 2017-05-28T22:37:49Z Empty follicle syndrome Empty follicle syndrome (EFS) has been defined as a condition in which no oocytes are retrieved from mature ovarian follicles with apparently normal follicular development and estradiol levels, after COH for an assisted reproductive technology (ART) cycle, despite repeated aspiration and flushing. A failure to collect oocytes after an apparently normal controlled ovarian hyperstimulation cycle for in vitro fertilization.