Variation in antimüllerian hormone concentration during the menstrual cycle may change the clinical classification of the ovarian response.

Objective: To assess the variability of antimüllerian hormone (AMH) concentrations in women with "adequate ovarian reserve" during unstimulated menstrual cycles and to determine the impact on clinical classifications.

Design: Pilot cohort study.

Setting: Private fertility clinic.

Patient(s): Twelve consecutive women (aged 29 to 43 years) referred to a fertility service, with AMH measurements repeated throughout unstimulated cycle, and who had at least one AMH measurement indicating "adequate ovarian reserve."

Intervention(s): None.

Main Outcome Measure(s): AMH concentrations assessed in 82 serum samples from 12 women compared against the published cutoffs for reduced ovarian reserve and for risk of excessive response to ovarian stimulation.

Result(s): Over half the women (7 of 12) were reclassified as a result of testing AMH concentrations at different phases of the menstrual cycle. Over one-third (4 or 5 of 12) crossed a cutoff for reduced ovarian reserve; 2 of 12 crossed cutoffs predicting hyperstimulation. There was a statistically significant change in AMH concentration according to the day of the cycle, with a negative trend of the median AMH concentration from the follicular to luteal phase. The maximum change in median AMH concentration over cycle was 7.9 pmol/L, and the mean difference between the maximum and minimum AMH was 6.7 pmol/L.

Conclusion(s): In this pilot study, the AMH concentration varied during menstrual cycle, and the clinical classification of the ovarian response was altered.