Antimullerian hormone (AMH) is a hormone whose value can be determined in a blood test to assess a woman's ovarian reserve. This hormone is produced by the antral follicles, so it is proportional to the antral follicle count and the number of eggs that can be obtained in an ovarian stimulation.
In general, AMH is considered to be the most reliable parameter for assessing ovarian reserve. However, sometimes we find that the values differ from one retrieval to another, and we can even find increases in its value over time. This increase is not related to an increase in ovarian reserve, as this decreases over time.
AMH can be highly variable due to factors such as seasonal changes, timing of the cycle, smoking or certain diseases. A study that assessed the variability of AMH on different days of the cycle found an average variation of up to 20%, being higher in women with low AMH levels.
Therefore, the information given by AMH should always be contrasted with an ultrasound of antral follicle count, and caution should be exercised when interpreting a single AMH determination, especially in the case of women with low ovarian reserve.