Inter-cycle and inter-observer variability of the antral follicle count in routine clinical practice

Antral follicle count (AFC) is a reliable predictor of ovarian response to stimulation and its inter-cycle and inter-observer variability has been extensively studied on in vitro fertilization (IVF), mostly in highly selected populations within studies not originally designed for this purpose. In this retrospective cohort study, we assess the inter-cycle variation of AFC in a setting similar to that of the daily practice. We included only patients undergoing mild stimulation for intrauterine insemination (IUI). One hundred and forty-eight patients had two (62 patients, group A), three (49 patients, group B) or four (37 patients, group C) IUI cycles and AFC was measured on early follicular phase of each cycle by one of the members of the medical team within daily practice. Intra-class correlation coefficients were used to estimate variability. Inter-cycle variability rendered ICCs above 0.70 in all groups improving along with the number of cycles [Group A ICC 0.78 (95%CI 0.66–0.86), Group B ICC 0.87 (95%CI 0.80–0.92) and Group C ICC 0.91 (95%CI 0.85–0.95)]. Inter-observer variability showed a high degree of concordance with ICCs above 0.95. We provide the closest approximation to real inter-cycle and inter-observer AFC variability expected in routine clinical practice.